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Materials, Volume 9, Issue 2 (February 2016) – 53 articles

Cover Story (view full-size image): The risk of infectious diseases can be diminished while using materials with antibacterial properties. PHMB is a good example of a strong, diverse, antimicrobial agent with low toxicity, which has attracted much attention for its effective antimicrobial finishing. This article presents the results concerning laminates with antimicrobial properties imparted by PHMB embedded in the MF resin. This work is the result of collaboration between the SONAE-Industria group and several Portuguese Universities. View the paper
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0 pages, 2742 KiB  
Article
RETRACTED: Porosity Defect Remodeling and Tensile Analysis of Cast Steel
by Linfeng Sun, Ridong Liao, Wei Lu and Sibo Fu
Materials 2016, 9(2), 119; https://doi.org/10.3390/ma9020119 - 22 Feb 2016
Cited by 1 | Viewed by 7741 | Retraction
Abstract
Tensile properties on ASTM A216 WCB cast steel with centerline porosity defect were studied with radiographic mapping and finite element remodeling technique. Non-linear elastic and plastic behaviors dependent on porosity were mathematically described by relevant equation sets. According to the ASTM E8 tensile [...] Read more.
Tensile properties on ASTM A216 WCB cast steel with centerline porosity defect were studied with radiographic mapping and finite element remodeling technique. Non-linear elastic and plastic behaviors dependent on porosity were mathematically described by relevant equation sets. According to the ASTM E8 tensile test standard, matrix and defect specimens were machined into two categories by two types of height. After applying radiographic inspection, defect morphologies were mapped to the mid-sections of the finite element models and the porosity fraction fields had been generated with interpolation method. ABAQUS input parameters were confirmed by trial simulations to the matrix specimen and comparison with experimental outcomes. Fine agreements of the result curves between simulations and experiments could be observed, and predicted positions of the tensile fracture were found to be in accordance with the tests. Chord modulus was used to obtain the equivalent elastic stiffness because of the non-linear features. The results showed that elongation was the most influenced term to the defect cast steel, compared with elastic stiffness and yield stress. Additional visual explanations on the tensile fracture caused by void propagation were also given by the result contours at different mechanical stages, including distributions of Mises stress and plastic strain. Full article
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Figure 1

Figure 1
<p>Hardening curve of the matrix material.</p> Full article ">Figure 2
<p>Experimental specimen and cast blank radiograph: (<b>a</b>) Dimensions of the specimen; (<b>b</b>) Selecting location of the matrix specimen.</p> Full article ">Figure 3
<p>Porosity fraction result: (<b>a</b>) Original radiograph; (<b>b</b>) Image of defect after shadow filtration; (<b>c</b>) Thickness distribution in the specimen; (<b>d</b>) Porosity fraction field distribution.</p> Full article ">Figure 4
<p>Images of tensile fracture location and initial porosity analysis of specimen A3: (<b>a</b>) Fracture location of A3; (<b>b</b>) Radiograph of porosity distribution along different distances from mid-length; (<b>c</b>) Cross section porosity distribution curve; (<b>d</b>) Fracture surface of A3.</p> Full article ">Figure 5
<p>Finite element (FE) mapping model: (<b>a</b>) Meshing details; (<b>b</b>) Computational FE model after mapping and remodeling.</p> Full article ">Figure 6
<p>Tensile test curves of the 11 specimens: (<b>a</b>) Complete tensile test curves for all specimens; (<b>b</b>) Stress-strain curves after scaling up for all specimens.</p> Full article ">Figure 7
<p>Tensile result comparison of the matrix specimen between test and simulation. (<b>a</b>) Complete tensile result curves; (<b>b</b>) Curves after scaling up.</p> Full article ">Figure 8
<p>Tensile result comparisons of the defect-containing specimens between test and simulation: (<b>a</b>) Specimen B1; (<b>b</b>) Specimen B2.</p> Full article ">Figure 9
<p>Comparisons of the fractures between test and simulation predicting: (<b>a</b>) Specimen A2; (<b>b</b>) Specimen A3.</p> Full article ">Figure 10
<p>Tensile performance on Specimen A3: (<b>a</b>) Locations of 3 examiningpoints (A, B and C), which represent different stages of strain; (<b>b</b>) Porosity propagation contours at three examining points (A, B and C); (<b>c</b>) Stress propagation contours; (<b>d</b>) Plastic strain propagation contours at three examining points (A, B and C).</p> Full article ">Figure 11
<p>Simulated development of averaged porosity and Mises stress with strain of Specimen A3.</p> Full article ">
3605 KiB  
Article
Investigation of Fumed Silica/Aqueous NaCl Superdielectric Material
by Natalie Jenkins, Clayton Petty and Jonathan Phillips
Materials 2016, 9(2), 118; https://doi.org/10.3390/ma9020118 - 20 Feb 2016
Cited by 9 | Viewed by 4923
Abstract
A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >108 over the full range of dielectric thicknesses of 0.38–3.9 mm and discharge times of 0.25–>100 s was [...] Read more.
A constant current charge/discharge protocol which showed fumed silica filled to the point of incipient wetness with aqueous NaCl solution to have dielectric constants >108 over the full range of dielectric thicknesses of 0.38–3.9 mm and discharge times of 0.25–>100 s was studied, making this material another example of a superdielectric. The dielectric constant was impacted by both frequency and thickness. For time to discharge greater than 10 s the dielectric constant for all thicknesses needed to be fairly constant, always >109, although trending higher with increasing thickness. At shorter discharge times the dielectric constant consistently decreased, with decreasing time to discharge. Hence, it is reasonable to suggest that for time to discharge >10 s the dielectric constant at all thicknesses will be greater than 109. This in turn implies an energy density for a 5 micron thick dielectric layer in the order of 350 J/cm3 for discharge times greater than 10 s. Full article
(This article belongs to the Section Energy Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Dielectric constant below 1 volt <span class="html-italic">vs.</span> level of NaCl saturation for fumed silica-based capacitors. The RC time constant method was employed to determine the dielectric constant of fumed silica/aqueous NaCl dielectric materials that differed substantially only in the level of salt concentration. For example, in all cases the dielectric thickness was 2 ± 0.2 mm. Relative saturation computation was based on 100% NaCl saturation at 25 °C: 360 g NaCl/1000 g H<sub>2</sub>O.</p> Full article ">Figure 2
<p>Example of raw, constant current data for capacitor 1. (<b>a</b>) Ten cycles, with a DT of ~9 s. (<b>b</b>) In this and all other cases dielectric constants computed for three regions, by voltage; I: 1.6–2.3; II: 0.8–1.6; and III: 0.1–0.8 V. These regions show nearly linear change in voltage for a constant current.</p> Full article ">Figure 2 Cont.
<p>Example of raw, constant current data for capacitor 1. (<b>a</b>) Ten cycles, with a DT of ~9 s. (<b>b</b>) In this and all other cases dielectric constants computed for three regions, by voltage; I: 1.6–2.3; II: 0.8–1.6; and III: 0.1–0.8 V. These regions show nearly linear change in voltage for a constant current.</p> Full article ">Figure 3
<p>Long time to discharge behavior. Shown is a slow discharge process (DT ~600 s) for capacitor 1, programmed to reach 1 volt. The maximum voltage attainable, for long DT, just over 1.1 V in this case, was at best 1.3 V, and to a good approximation the capacitance is constant over the entire discharge.</p> Full article ">Figure 4
<p>Dielectric constant 0.8–0.1 Volts. (<b>a</b>) Dielectric constants measured for DT of less than 120 s. (<b>b</b>) Dielectric constants measured for DT less than 12 s. The thickness of the dielectric layer is shown in the figure key.</p> Full article ">Figure 5
<p>Dielectric constant as a function of DT, three voltage regions, capacitor 3. Dielectric constants were computed for three voltage regions, as described in the text. The highest dielectric constant, and ~60% of the energy, is found below 0.8 V. All four capacitors displayed a similar pattern of deceasing dielectric value with increasing voltage and decreasing DT.</p> Full article ">Figure 6
<p>Power as a function of thickness and DT. (<b>a</b>) Power density (total energy released in one discharge divided by DT × dielectric volume) increases as the dielectric layer thickness decreases. For DT greater than ~20 s power is nearly constant for any dielectric thicknesses. (<b>b</b>) DT values less than 12 s. The delivered power increases as discharge is done more rapidly.</p> Full article ">Figure 7
<p>Energy density as a function of DT and dielectric thickness. (<b>a</b>) For discharge times up to 120 s. Energy density decreases very slowly for DT &gt; 10 s; (<b>b</b>) For discharge times less than 12 s. This clearly shows energy density drops sharply for DT &lt; 2 s.</p> Full article ">Figure 8
<p>Relative capacitance as a function of time. As shown the capacitance decreases steadily for the first 150 h, and then stabilizes. All three capacitive regions, 0.8–0.1 V, 1.6–0.8 V, and 2.3–1.6 V loose capacitance at roughly the same rate.</p> Full article ">Figure 9
<p>Open circuit voltage. There is clearly a dramatic change in internal resistance at approximately 1.2 V, the voltage of water decomposition.</p> Full article ">Figure 10
<p>Testing geometry galvanostat: A—Dielectric Material, variable thickness; B—Grafoil electrodes, 0.04 cm thick × 5 cm diameter; C—Grafoil “wires”, ~10 cm length; D—Galvanastat (BioLogic 300); E—1 liter volume zip lock plastic bag; F—DI water-saturated paper towel.</p> Full article ">
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Article
Tribo-Mechanical Properties of HVOF Deposited Fe3Al Coatings Reinforced with TiB2 Particles for Wear-Resistant Applications
by Mahdi Amiriyan, Carl Blais, Sylvio Savoie, Robert Schulz, Mario Gariépy and Houshang Alamdari
Materials 2016, 9(2), 117; https://doi.org/10.3390/ma9020117 - 19 Feb 2016
Cited by 18 | Viewed by 5431
Abstract
This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy [...] Read more.
This study reveals the effect of TiB2 particles on the mechanical and tribological properties of Fe3Al-TiB2 composite coatings against an alumina counterpart. The feedstock was produced by milling Fe3Al and TiB2 powders in a high energy ball mill. The high-velocity oxy-fuel (HVOF) technique was used to deposit the feedstock powder on a steel substrate. The effect of TiB2 addition on mechanical properties and dry sliding wear rates of the coatings at sliding speeds ranging from 0.04 to 0.8 m·s−1 and loads of 3, 5 and 7 N was studied. Coatings made from unreinforced Fe3Al exhibited a relatively high wear rate. The Vickers hardness, elastic modulus and wear resistance of the coatings increased with increasing TiB2 content in the Fe3Al matrix. The wear mechanisms strongly depended on the sliding speed and the presence of TiB2 particles but were less dependent on the applied load. Full article
(This article belongs to the Section Advanced Composites)
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Figure 1

Figure 1
<p>XRD patterns of the (<b>a</b>) Fe<sub>3</sub>Al-30 vol.% TiB<sub>2</sub> and (<b>b</b>) Fe<sub>3</sub>Al-50 vol.% TiB<sub>2</sub> HVOF composite coatings.</p> Full article ">Figure 2
<p>Cross-sectional backscattered SEM images of the unreinforced (0 vol.% TiB<sub>2</sub>) Fe<sub>3</sub>Al (<b>a</b> and <b>a’</b>), 30 (<b>b</b> and <b>b’</b>) and 50 (<b>c</b> and <b>c’</b>) vol.% TiB<sub>2</sub> coatings. The arrow on a’ indicates a pore.</p> Full article ">Figure 3
<p>EDS spectra of the (<b>a</b>) main grey phase in Fe<sub>3</sub>Al coating, (<b>b</b>) dark grey oxide inclusions, (<b>c</b>) light grey areas and (<b>d</b>) TiB<sub>2</sub> particles.</p> Full article ">Figure 4
<p>Hardness of the substrate and coatings as a function of different TiB<sub>2</sub> content.</p> Full article ">Figure 5
<p>Typical load-displacement curves of the coatings.</p> Full article ">Figure 6
<p>SEM images of Vickers indentation cracks (induced at high load of 1000 gf) on (<b>a</b>) Fe<sub>3</sub>Al, (<b>b</b>) Fe<sub>3</sub>Al-30 vol.% TiB<sub>2</sub> and (<b>c</b>) Fe<sub>3</sub>Al-50 vol.% TiB<sub>2</sub> coating cross sections. Crack propagation paths have been indicated by white ovals.</p> Full article ">Figure 7
<p>Typical friction coefficient curve for a thermally sprayed Fe<sub>3</sub>Al coating.</p> Full article ">Figure 8
<p>Friction coefficient <span class="html-italic">versus</span> sliding speed at the applied load of 5 N.</p> Full article ">Figure 9
<p>Wear rates as a function of sliding speed and applied load. (<b>a</b>) Fe<sub>3</sub>Al coatings and (<b>b</b>–<b>d</b>) composite coatings.</p> Full article ">Figure 10
<p>SEM images at different magnifications of the worn surfaces for Fe<sub>3</sub>Al at a sliding speed of (<b>a</b> and <b>a’</b>) 0.04, (<b>b</b> and <b>b’</b>) 0.1 and (<b>c</b> and <b>c’</b>) 0.8 m·s<sup>−1</sup> under a load of 5 N. EDS was taken from the points marked by X.</p> Full article ">Figure 10 Cont.
<p>SEM images at different magnifications of the worn surfaces for Fe<sub>3</sub>Al at a sliding speed of (<b>a</b> and <b>a’</b>) 0.04, (<b>b</b> and <b>b’</b>) 0.1 and (<b>c</b> and <b>c’</b>) 0.8 m·s<sup>−1</sup> under a load of 5 N. EDS was taken from the points marked by X.</p> Full article ">Figure 11
<p>EDS spectra of the worn surface of Fe<sub>3</sub>Al coating at (<b>a</b>) 0.04 and (<b>b</b>) 0.8 m·s<sup>−1</sup>.</p> Full article ">Figure 12
<p>SEM images at different magnifications of the alumina counterpart used against Fe<sub>3</sub>Al at a sliding speed of (<b>a</b> and <b>a’</b>) 0.04, (<b>b</b> and <b>b’</b>) 0.1, (<b>c</b> and <b>c’</b>) 0.3 and (<b>d</b> and <b>d’</b>) 0.8 m·s<sup>−1</sup>; (<b>a”</b>) EDS spectrum of the alumina ball and (<b>d”</b>) EDS spectrum of the transferred layer obtained at the highest speed under a load of 5 N. EDS was taken from the points marked by X.</p> Full article ">Figure 13
<p>SEM images at different magnifications of the worn surfaces for Fe<sub>3</sub>Al-50 vol.% TiB<sub>2</sub> at a sliding speed of (<b>a</b> and <b>a’</b>) 0.04, (<b>b</b> and <b>b’</b>) 0.1, (<b>c</b> and <b>c’</b>) 0.3 and (<b>d</b> and <b>d’</b>) 0.8 m·s<sup>−1</sup> under a load of 5 N.</p> Full article ">Figure 14
<p>Microscopic morphologies of the wear debris of the Fe<sub>3</sub>Al-TiB<sub>2</sub> composite coatings worn at sliding speed of (<b>a</b>) 0.04 and (<b>b</b>) 0.3 m·s<sup>−1</sup>.</p> Full article ">Figure 15
<p>SEM images at different magnifications of the alumina counterpart used against Fe<sub>3</sub>Al-50 vol.% TiB<sub>2</sub> at a sliding speed of (<b>a</b> and <b>a’</b>) 0.04, (<b>b</b> and <b>b’</b>) 0.3 and (<b>c</b> and <b>c’</b>) 0.8 m·s<sup>−1</sup> under 5 N load.</p> Full article ">
10818 KiB  
Review
Bio-Inspired Extreme Wetting Surfaces for Biomedical Applications
by Sera Shin, Jungmok Seo, Heetak Han, Subin Kang, Hyunchul Kim and Taeyoon Lee
Materials 2016, 9(2), 116; https://doi.org/10.3390/ma9020116 - 19 Feb 2016
Cited by 109 | Viewed by 17547
Abstract
Biological creatures with unique surface wettability have long served as a source of inspiration for scientists and engineers. More specifically, materials exhibiting extreme wetting properties, such as superhydrophilic and superhydrophobic surfaces, have attracted considerable attention because of their potential use in various applications, [...] Read more.
Biological creatures with unique surface wettability have long served as a source of inspiration for scientists and engineers. More specifically, materials exhibiting extreme wetting properties, such as superhydrophilic and superhydrophobic surfaces, have attracted considerable attention because of their potential use in various applications, such as self-cleaning fabrics, anti-fog windows, anti-corrosive coatings, drag-reduction systems, and efficient water transportation. In particular, the engineering of surface wettability by manipulating chemical properties and structure opens emerging biomedical applications ranging from high-throughput cell culture platforms to biomedical devices. This review describes design and fabrication methods for artificial extreme wetting surfaces. Next, we introduce some of the newer and emerging biomedical applications using extreme wetting surfaces. Current challenges and future prospects of the surfaces for potential biomedical applications are also addressed. Full article
(This article belongs to the Special Issue Superhydrophobicity of Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Various natural extreme wetting surfaces and their potential biomedical applications. Lotus leaf (image by Tanakawho, reproduced under Creative Commons Attribution (CC BY) license); Namib beetle (image by James Anderson, reproduced under Creative Commons Attribution Non-commercial Share-alike (CC BY-NC-SA) license); Pitcher plant (image by Bauer, reproduced under CC BY); Biomedical device (image from the School of Natural Resources &amp; Environment, University of Michigan, reproduced under CC BY license); Lab-on-a-chip (image from Argonne National Laboratory, reproduced under CC BY-NC-SA license); and others (public domain photo and images).</p> Full article ">Figure 2
<p>Schematic representations of a water droplet on flat and rough solid surfaces. (<b>a</b>) A droplet on an ideal flat surface; (<b>b</b>) A droplet in the Wenzel state, in which the rough surface is fully wetted; (<b>c</b>) A droplet in the Cassie-Baxter state, in which air pockets form at the interface between the non-wetted rough surface and droplet.</p> Full article ">Figure 3
<p>(<b>a</b>) Image of a lotus leaf (image by GJ Bulte, reproduced under Creative Commons Attribution Share-alike (CC BY-SA) license); (<b>b</b>) the corresponding scanning electron microscopy (SEM) image showing the hierarchical micro/nanostructures comprising papillose cells; (<b>c</b>) SEM image of a microsphere/single-walled carbon nanotube (CNT) composite array; (<b>d</b>) SEM image of a tetragonal array comprising Cu microprotrusions covered by nanostructured Ag dendrites; (<b>e</b>) Photograph of rose petals exhibiting water-adhesive properties; and (<b>f</b>) SEM image of rose petal surface (image by Audrey, reproduced under CC BY license); (<b>g</b>) SEM image of a rose petal-like polystyrene (PS)-film, onto which a water droplet was pinned even when turned upside down; (<b>h</b>) SEM image of Si nanowire arrays; Inset: water droplet deposited on the array after rapid thermal annealing (RTA) at tilt angle of 180°. Reproduced from [<a href="#B32-materials-09-00116" class="html-bibr">32</a>,<a href="#B34-materials-09-00116" class="html-bibr">34</a>,<a href="#B61-materials-09-00116" class="html-bibr">61</a>,<a href="#B62-materials-09-00116" class="html-bibr">62</a>,<a href="#B63-materials-09-00116" class="html-bibr">63</a>,<a href="#B64-materials-09-00116" class="html-bibr">64</a>] with the permission by Springer, Copyright 1997 and by ACS Publications, Copyright 2007, 2008, 2013 and by Elsevier, Copyright 2013.</p> Full article ">Figure 4
<p>(<b>a</b>) Bidirectional anisotropic wetting of a rice leaf (<span class="html-italic">Oryza sativa</span>): (<b>i</b>) Photograph and SEM images of the rice leaf; (<b>ii</b>) Optical profiler height map of the rice leaf; (<b>iii</b>) Bidirectional anisotropic wetting behavior; (<b>b</b>) Unidirectional wetting behavior of a butterfly wing (<span class="html-italic">Blue Morpho didius</span>): (<b>i</b>) Photograph and SEM images of the Blue Morpho didius butterfly wing; (<b>ii</b>) optical profiler height map of the butterfly wing; and (<b>iii</b>) unidirectional anisotropic wetting behavior; (<b>c</b>) Droplet motion on poly(p-xylylene) film of tilted nanorods; and (<b>d</b>) corresponding time-lapse frames of droplet motion. Reproduced from [<a href="#B66-materials-09-00116" class="html-bibr">66</a>,<a href="#B67-materials-09-00116" class="html-bibr">67</a>] with the permission by Royal Society of Chemistry, Copyright 2012 and by Nature Publishing Group, Copyright 2010.</p> Full article ">Figure 5
<p>(<b>a</b>) Water-capturing surfaces of fused <span class="html-italic">Stenocara</span> beetle overwings: (<b>i</b>) Photograph and SEM images of wax-stained (colored) and unstained beetle wing regions (wax-free; black); (<b>ii</b>) Time-dependent growth of water droplets in a fog-laden wind; (<b>b</b>) Hydrophilic-patterned superhydrophobic Si nanowire (NW) arrays for water droplet guiding: (<b>i</b>) Fabrication of tilted Si NW arrays featuring a water guiding track; (<b>ii</b>) Sequential photographs of a water droplet guided along the hydrophilic track. Reproduced from [<a href="#B12-materials-09-00116" class="html-bibr">12</a>,<a href="#B77-materials-09-00116" class="html-bibr">77</a>] with permission by Nature Publishing Group, Copyright 2010 and by ACS Publications, Copyright 2011.</p> Full article ">Figure 6
<p>(<b>a</b>) Image of the <span class="html-italic">Nepenthes</span> pitcher plant (image by William Warby, reproduced under CC BY) and SEM images of the peristome surface and inner wall. The surface presents radial ridges, while the inner wall is covered with waxy crystals; (<b>b</b>) (<b>i</b>) Slippery film fabrication; (<b>ii</b>) Optical micrographs of a sliding hexane drop at a low angle; (<b>c</b>) Porous matrix formation on an elastic PDMS film and photographs of dry and lubricated substrates; (<b>d</b>) (<b>i</b>) Mechanically induced topographical changes in a liquid slippery film upon stretching and (<b>ii</b>) corresponding droplet motions; (<b>e</b>) Sequential photographs of oil droplet movement on the dynamic slippery surface. Reproduced from [<a href="#B13-materials-09-00116" class="html-bibr">13</a>,<a href="#B93-materials-09-00116" class="html-bibr">93</a>,<a href="#B94-materials-09-00116" class="html-bibr">94</a>] with permission by National Academy of Sciences of the USA, Copyright 2004 and by Nature Publishing Group, Copyright 2011, 2013.</p> Full article ">Figure 7
<p>(<b>a</b>) Switchable adhesion under UV and visible light irradiation; (<b>b</b>) Reversible adhesion of superhydrophobic azobenzene liquid crystal polymer (LCP) film; (<b>c</b>) (<b>i</b>) Volume expansion of Pd layers deposited on the Si NW arrays under atmospheric and H<sub>2</sub> ambient conditions; (<b>ii</b>) Contact angles (CAs) of the Pd-coated Si NW arrays showing superhydrophobicity under atmospheric and H<sub>2</sub> conditions; (<b>d</b>) Time-lapse photographs of a moving water droplet on Pd-coated Si NW arrays under atmospheric and H<sub>2</sub> conditions. Reproduced from [<a href="#B98-materials-09-00116" class="html-bibr">98</a>,<a href="#B99-materials-09-00116" class="html-bibr">99</a>] with the permission by Royal Society of Chemistry, Copyright 2012 and by John Wiley and Sons, Copyright 2013.</p> Full article ">Figure 8
<p>(<b>a</b>) (<b>i</b>) Three-dimensional (3D) hydrogel array on hydrophilic patterned spots; (<b>ii</b>) The images before and after 24 h of immersion in culture medium of alginate based 3D hydrogels; (<b>b</b>) Fluorescent microscopy images of live (green)/dead (red) cells in the 24 different hydrogels after 24 h of cell culture. Reproduced from [<a href="#B120-materials-09-00116" class="html-bibr">120</a>] with permission by Royal Society of Chemistry, Copyright 2012.</p> Full article ">Figure 9
<p>(<b>a</b>) (<b>i</b>) Hanging drop culture on the indentation-patterned superhydrophobic surface; (<b>ii</b>) Live (green)/dead (red) cell ratios 24 h after the addition of various doxorubicin concentrations for densities of 30,000 (left bar) and 40,000 (right bar) cells/droplet; (<b>iii</b>) Fluorescent images of L929 spheroids in the presence of doxorubicin (<b>ii</b>); (<b>b</b>) (<b>i</b>) Culture medium droplets adhered on the H<sub>2</sub>-exposed Pd-coated Si NWs for different tile angle (0°, 90°, and 180°) and medium volumes (5, 10, 15 and 20 μL); (<b>ii</b>) Live/dead cell staining, size distribution, and vascular endothelial growth factor (VEGF) protein secretion from spheroids after 4 days of culture at various cell densities and medium volumes. Reproduced from [<a href="#B18-materials-09-00116" class="html-bibr">18</a>,<a href="#B136-materials-09-00116" class="html-bibr">136</a>] with permission by John Wiley and Sons, Copyright 2014.</p> Full article ">Figure 10
<p>(<b>a</b>) The bacterial growth on the PS and polycarbonate (PC) structured and flat substrates; (<b>b</b>) (<b>i</b>) Blood repellency on slippery tethered-liquid perfluorocarbon (TLP)-coated surfaces; (<b>ii</b>) Photographs of a sliding blood droplet on the slippery surface; (<b>c</b>) (<b>i</b>) Fluorescent micrographs of fibrinogen on acrylic or polysulfone surfaces with or without TLP coating; (<b>ii</b>) Photographs of polyurethane cannulae, polycarbonate connectors, and PVC tubing with (top) or without (bottom) TLP coating after 8 h of blood flow. Reproduced from [<a href="#B148-materials-09-00116" class="html-bibr">148</a>] under CC BY license. Reproduced from [<a href="#B152-materials-09-00116" class="html-bibr">152</a>] with permission by Nature Publishing Group, Copyright 2014.</p> Full article ">Figure 11
<p>(<b>a</b>) (<b>i</b>) Droplet motion and mixing on a pDA micropatterned slippery device; (<b>ii</b>) Chemical reaction in organic solvent (THF) on the slippery device; (<b>b</b>) (<b>i</b>) Manipulation of water motions such as moving, mixing and analysis on a suspended PDMS substrate with micro-pillar arrays; (<b>ii</b>) SEM image of the dimple structure; (<b>iii</b>) Photograph of a water droplet on the PDMS substrate; (<b>c</b>) (<b>i</b>) Surface-enhanced Raman spectroscopy (SERS) measurement system; (<b>ii</b>) Small interfering RNA-lipidoid complex formation; (<b>d</b>) <span class="html-italic">in situ/ex situ</span> SERS analysis spectra at different concentrations of Rhodamine 6G (R6G) for R6G/Ag nanoparticle (NP) droplet mixture and an evaporated R6G/Ag NP droplet, respectively; (<b>e</b>) Fluorescent images and flow cytometry analyses of green fluorescent protein (GFP)-HeLa cells after transfection. Reproduced from [<a href="#B166-materials-09-00116" class="html-bibr">166</a>,<a href="#B167-materials-09-00116" class="html-bibr">167</a>] with permission by American Chemical Society, Copyright 2014, and permission by Nature Publishing Group, Copyright 2015.</p> Full article ">Figure 12
<p>(<b>a</b>) High-throughput screening platform using a superhydrophobic surface patterned with hydrophilic spots; (<b>b</b>) (<b>i</b>) Superhydrophobic surface patterned with hydrophilic rings for high-throughput assay; (<b>ii</b>) Hydrogel- and phosphate-buffered saline (PBS) droplet-loaded substrate; (<b>iii</b>) Surface plots of release profiles of the fluorescein isothiocyanate labeled bovine serum albumin (BSA-FITC) from alginate hydrogels obtained by the acquisition of fluorescent microscopy images. Reproduced from [<a href="#B19-materials-09-00116" class="html-bibr">19</a>,<a href="#B173-materials-09-00116" class="html-bibr">173</a>] with permission by American Chemical Society, Copyright 2011, 2013.</p> Full article ">
8212 KiB  
Article
Structure and Compressive Properties of Invar-Cenosphere Syntactic Foams
by Dung Luong, Dirk Lehmhus, Nikhil Gupta, Joerg Weise and Mohamed Bayoumi
Materials 2016, 9(2), 115; https://doi.org/10.3390/ma9020115 - 18 Feb 2016
Cited by 31 | Viewed by 8670
Abstract
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately [...] Read more.
The present study investigates the mechanical performance of syntactic foams produced by means of the metal powder injection molding process having an Invar (FeNi36) matrix and including cenospheres as hollow particles at weight fractions (wt.%) of 5 and 10, respectively, corresponding to approximately 41.6 and 60.0 vol.% in relation to the metal content and at 0.6 g/cm3 hollow particle density. The synthesis process results in survival of cenospheres and provides low density syntactic foams. The microstructure of the materials is investigated as well as the mechanical performance under quasi-static and high strain rate compressive loads. The compressive stress-strain curves of syntactic foams reveal a continuous strain hardening behavior in the plastic region, followed by a densification region. The results reveal a strain rate sensitivity in cenosphere-based Invar matrix syntactic foams. Differences in properties between cenosphere- and glass microsphere-based materials are discussed in relation to the findings of microstructural investigations. Cenospheres present a viable choice as filler material in iron-based syntactic foams due to their higher thermal stability compared to glass microspheres. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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<p>Approximate quantitative comparison of aluminum, titanium, zinc and steel conventional and SFs’ (syntactic foams) compressive strength and density, based on a data collection by Weise <span class="html-italic">et al.</span> [<a href="#B17-materials-09-00115" class="html-bibr">17</a>].</p> Full article ">Figure 2
<p>SEM images of fracture surfaces of SFs based on glass microspheres with matrices of Invar (FeNi36, (<b>a</b>)) and 316L (<b>b</b>)—glass inclusions within the matrix are visible in both cases. S60HS represents S60 hollow glass microspheres manufactured by 3M, St. Paul, MN, USA [<a href="#B24-materials-09-00115" class="html-bibr">24</a>].</p> Full article ">Figure 3
<p>Optical micrographs of (<b>a</b>,<b>c</b>) Invar-5CS; and (<b>b</b>,<b>d</b>) Invar-10CS at different magnifications.</p> Full article ">Figure 4
<p>SEM images of (<b>a</b>) Fillite 106 alumino-silicate cenospheres in their virgin state before processing; and (<b>b</b>) embedded in the Invar-10CS after feedstock processing, injection molding and sintering.</p> Full article ">Figure 5
<p>Representative of the compressive stress-strain response of: (<b>a</b>) Invar-5CS; and (<b>b</b>) Invar-10CS at strain rate of 10<sup>−2</sup>, 10<sup>−3</sup> and 10<sup>−4</sup>·s<sup>−1</sup>.</p> Full article ">Figure 6
<p>The compressive response of (<b>a</b>) Invar-5CS; and (<b>b</b>) Invar-10CS at high strain rate loading in comparison to the quasi-static loading.</p> Full article ">Figure 7
<p>The compressive stress-strain response of Invar steel and its SFs at the strain rate of 10<sup>−3</sup>·s<sup>−1</sup>. The data of Invar and its SFs-filled glass microballoons (GM) is obtained from reference [<a href="#B20-materials-09-00115" class="html-bibr">20</a>].</p> Full article ">Figure 8
<p>The yield strength of Invar SFs-filled cenospheres in comparison to other steel based matrix SFs. The data is generated and collected from references [<a href="#B13-materials-09-00115" class="html-bibr">13</a>,<a href="#B14-materials-09-00115" class="html-bibr">14</a>,<a href="#B17-materials-09-00115" class="html-bibr">17</a>,<a href="#B20-materials-09-00115" class="html-bibr">20</a>,<a href="#B21-materials-09-00115" class="html-bibr">21</a>,<a href="#B22-materials-09-00115" class="html-bibr">22</a>,<a href="#B28-materials-09-00115" class="html-bibr">28</a>,<a href="#B29-materials-09-00115" class="html-bibr">29</a>,<a href="#B30-materials-09-00115" class="html-bibr">30</a>,<a href="#B31-materials-09-00115" class="html-bibr">31</a>].</p> Full article ">Figure 9
<p>The plateau onset stress over density of Invar SFs in comparison to the yield strength over density of Invar matrix materials. The data of Invar SFs-filled glass microballoons is reported in reference [<a href="#B20-materials-09-00115" class="html-bibr">20</a>].</p> Full article ">Figure 10
<p>SEM images showing the cenosphere fracture in: (<b>a</b>) Invar-5CS; and (<b>b</b>) Invar-10CS at a strain of 5%.</p> Full article ">Figure 11
<p>The pattern of crack development on cenospheres under quasi-static loading in the top-bottom direction.</p> Full article ">Figure 12
<p>SEM images of fracture face on the Invar-10CS under quasi-static loading at magnification of (<b>a</b>) ×400; and (<b>b</b>) ×1500.</p> Full article ">Figure 13
<p>The energy absorption up to the strain of 50% of steel-based matrix SFs.</p> Full article ">Figure 14
<p>Stresses of (<b>a</b>) Invar-5CS; and (<b>b</b>) Invar-10CS at the strain from 5% to 25% plotted over strain rate.</p> Full article ">Figure 15
<p>Comparison between the experimental and prediction results of: (<b>a</b>,<b>c</b>,<b>e</b>) Invar-5CS; and (<b>b</b>,<b>d</b>,<b>f</b>) Invar-10CS at different strain rates.</p> Full article ">Figure 15 Cont.
<p>Comparison between the experimental and prediction results of: (<b>a</b>,<b>c</b>,<b>e</b>) Invar-5CS; and (<b>b</b>,<b>d</b>,<b>f</b>) Invar-10CS at different strain rates.</p> Full article ">Figure 16
<p>The metal powder injection molding (MIM) process of Invar SFs.</p> Full article ">
2147 KiB  
Article
Tailored N-Containing Carbons as Catalyst Supports in Alcohol Oxidation
by Sebastiano Campisi, Stefania Marzorati, Paolo Spontoni, Carine E. Chan-Thaw, Mariangela Longhi, Alberto Villa and Laura Prati
Materials 2016, 9(2), 114; https://doi.org/10.3390/ma9020114 - 17 Feb 2016
Cited by 5 | Viewed by 4877
Abstract
The introduction of N-containing functionalities in carbon-based materials is brought to stable and highly active metal-supported catalysts. However, up to now, the role of the amount and the nature of N-groups have not been completely clear. This study aims to clarify these aspects [...] Read more.
The introduction of N-containing functionalities in carbon-based materials is brought to stable and highly active metal-supported catalysts. However, up to now, the role of the amount and the nature of N-groups have not been completely clear. This study aims to clarify these aspects by preparing tailored N-containing carbons where different N-groups are introduced during the synthesis of the carbon material. These materials were used as the support for Pd nanoparticles. Testing these catalysts in alcohol oxidations and comparing the results with those obtained using Pd nanoparticles supported on different N-containing supports allowed us to obtain insight into the role of the different N-containing groups. In the cinnamyl alcohol oxidation, pyridine-like groups seem to favor both activity and selectivity toward cinnamaldehyde. Full article
(This article belongs to the Special Issue Porous Carbonaceous Materials from Biomass)
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<p>Different N-containing groups possibly present in carbons.</p> Full article ">Figure 2
<p>Isotherms of (<b>a</b>) GaG600 and (<b>b</b>) GaG900.</p> Full article ">Figure 3
<p>Porosity distribution (area-desorption part of the isotherm).</p> Full article ">Figure 4
<p>N1s analyses for GaG600 (<b>a</b>), GaG900 (<b>b</b>), Pd/GaG600 (<b>c</b>), and Pd/GaG900 (<b>d</b>), showing the presence of pyridinic (A), pyrrolic (B), pyridine oxide (C) and nitro-type nitrogen (D).</p> Full article ">Figure 5
<p>TEM representative image of Pd/GAG600.</p> Full article ">
13165 KiB  
Article
An in Vitro Twist Fatigue Test of Fabric Stent-Grafts Supported by Z-Stents vs. Ringed Stents
by Jing Lin, Robert Guidoin, Jia Du, Lu Wang, Graeham Douglas, Danjie Zhu, Mark Nutley, Lygia Perron, Ze Zhang and Yvan Douville
Materials 2016, 9(2), 113; https://doi.org/10.3390/ma9020113 - 16 Feb 2016
Cited by 18 | Viewed by 8486
Abstract
Whereas buckling can cause type III endoleaks, long-term twisting of a stent-graft was investigated here as a mechanism leading to type V endoleak or endotension. Two experimental device designs supported with Z-stents having strut angles of 35° or 45° were compared to a [...] Read more.
Whereas buckling can cause type III endoleaks, long-term twisting of a stent-graft was investigated here as a mechanism leading to type V endoleak or endotension. Two experimental device designs supported with Z-stents having strut angles of 35° or 45° were compared to a ringed control under accelerated twisting. Damage to each device was assessed and compared after different durations of twisting, with focus on damage that may allow leakage. Stent-grafts with 35° Z-stents had the most severe distortion and damage to the graft fabric. The 45° Z-stents caused less fabric damage. However, consistent stretching was still seen around the holes for sutures, which attach the stents to the graft fabric. Larger holes may become channels for fluid percolation through the wall. The ringed stent-graft had the least damage observed. Stent apexes with sharp angles appear to be responsible for major damage to the fabrics. Device manufacturers should consider stent apex angle when designing stent-grafts, and ensure their devices are resistant to twisting. Full article
(This article belongs to the Section Advanced Materials Characterization)
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<p>Twisting in explanted Talent stent-grafts. The area of the crotch of the bifurcation holds an irregular encapsulation, likely to prevent blood endoleak (<b>A</b>). The twisting can, however, be more evidenced (<b>B</b>: arrows) and results in fluid percolation (<b>C</b>: arrows).</p> Full article ">Figure 2
<p>The phenomenon of twisting is well evidenced in an explanted thoracic Zenith stent-graft (<b>A</b>: arrows); showing some fluid percolation at the twisting site (<b>B</b>: arrows).</p> Full article ">Figure 3
<p>Deformation from twisting in the body of an explanted Anaconda device is maintained after explantation. The fabric preserves its imperviousness according to the gross observation (<b>A</b>). However, endoleaks were shown in the distal limb (<b>B</b>).</p> Full article ">Figure 4
<p>Gross observations after twisting tests. The fabrics of the polyester conduits are without visible holes. However, some sutures are fractured in the Z-stent devices and one vertical strut of a 45° Z-stent is fractured after 168 h of accelerated testing.</p> Full article ">Figure 5
<p>Twist simulations for 24 h. There is no different in damage from fatigue to either Z-stent-graft. Neither stents nor sutures are broken, but the suture holes are enlarged. After the sutures are cut, abrasion is visible at the apex of the 35° stent. The device, stents, and fabric are intact in the ringed stent-graft. (<b>A1</b>,<b>B1</b>,<b>C1</b>) Gross observations; (<b>A2</b>,<b>B2</b>,<b>C2</b>) Observation in light microscopy with low magnification (10×); (<b>A3</b>,<b>B3</b>,<b>C3</b>) Observation in light microscopy with high magnification (40×); (<b>A4</b>,<b>B4</b>,<b>C4</b>) Observation in SEM (100×).</p> Full article ">Figure 6
<p>Twist simulations for 48 h. The fabrics of the stent-grafts supported by Z-stents were more severely abraded than the fabric of the ringed stent-graft. Broken sutures are found in the 35° Z-stents. The SEM confirms the best resistance to fabric abrasion by the ringed stent-grafts, and the enlarged suture holes in this device (<b>C4</b>). (<b>A1</b>,<b>B1</b>,<b>C1</b>) Gross observations; (<b>A2</b>,<b>B2</b>,<b>C2</b>) Observation in light microscopy with low magnification (10×); (<b>A3</b>,<b>B3</b>,<b>C3</b>) Observation in light microscopy with high magnification (40×); (<b>A4</b>,<b>B4</b>,<b>C4</b>) Observation in SEM (100×).</p> Full article ">Figure 7
<p>Twist tests of stent-grafts after 168 h. The stent-grafts supported by Z-stents are damaged to various levels. No holes are observed but a vertical strut of S5 is broken and numerous sutures are broken. The abrasion of the fabric is visible in the Z-stent devices, whereas it is well preserved in the ringed stent-grafts. (<b>A1</b>,<b>B1</b>,<b>C1</b>) Gross observations; (<b>A2</b>,<b>B2</b>,<b>C2</b>) Observation in light microscopy with low magnifications; (<b>A3</b>,<b>B3</b>,<b>C3</b>) Observation in light microscopy with high magnification (40×); (<b>A4</b>,<b>B4</b>,<b>C4</b>) Observation in SEM (100×).</p> Full article ">Figure 8
<p>Fabric counts of the fabrics of the stent-grafts. Both the warp and the weft counts decrease slightly after twisting simulation. (<b>A1</b>) 35° Z-stent; (<b>B1</b>) 45° Z-stent; (<b>C1</b>) Ringed stent.</p> Full article ">Figure 9
<p>Thickness and mass of the fabrics of the stent-grafts. (<b>A1</b>) 35° Z-stent; (<b>B1</b>) 45° Z-stent; (<b>C1</b>) Ringed stent.</p> Full article ">Figure 10
<p>Porosity of the fabrics of the stent-grafts.</p> Full article ">Figure 11
<p>Tensile strength of fibers from the stent-grafts after different test durations. (<b>A1</b>) 35° Z-stent; (<b>B1</b>) 45° Z-stent; (<b>C1</b>) Ringed stent.</p> Full article ">Figure 12
<p>Crystallinity of the polyester in the stent-grafts. After 168 h of twisting, crystallinity was decreased by up to 10% in the Z-stent devices, compared to less than 2% in the ringed–stent devices. (<b>A</b>) 35° and 45° Z-stent; (<b>B</b>) Ringed stent.</p> Full article ">Figure 13
<p>Endurant stent-graft. The fabric of the body and the limbs are supported by M-stents (<b>A</b>). Twisting might still exist in the vicinity of the crotch at the bifurcation (<b>A</b>: arrow), which is shown magnified (<b>B</b>).</p> Full article ">Figure 14
<p>Thin wall Cook LP. Compared to the bifurcated stent-graft, the straight tubular device is less vulnerable to damage from twisting (<b>A</b>). Though the moderate angles of the Z-stents are less likely to damage the fabric, twisting may not be completely eliminated in cases with poor device deployment or complex anatomy. This could cause concentration of twisting in the unsupported fabric between two adjacent Z-stents (<b>B</b>).</p> Full article ">Figure 15
<p>Comparison of the experimental devices to commercially available stent-grafts. They have water permeability similar to those of multifilament devices, whereas the Talent stent-graft has the highest permeability.</p> Full article ">Figure 16
<p>Z-stent <span class="html-italic">vs.</span> ringed stent. The two Z-stents were assembled in our laboratory. The seamless woven fabric tube (1.0 cm diameter and 10 cm long) was supported by Z-stents, held together by a vertical strut and sutured externally to the fabric. The apex angles of the two Z-stents were 35° (<b>A1</b>,<b>A2</b>,<b>A3</b>,<b>A4</b>) and 45° (<b>B1</b>,<b>B2</b>,<b>B3</b>,<b>B4</b>), respectively. The ringed stent-graft was a commercially available device (Anaconda), externally supported by 27 ringed stents, individually sutured to the seamless woven fabric tube (1.0 cm diameter and 10 cm long) (<b>C1</b>,<b>C2</b>,<b>C3</b>,<b>C4</b>).</p> Full article ">Figure 17
<p>The fatigue machine developed at Donghua University simulates the twisting observed for stent-grafts <span class="html-italic">in vivo</span>. It mimics the pulsatile dynamics within human tortuous iliac arteries (<b>A</b>). The device is attached by its first extremity to a fixed vertical metallic pipe. The second extremity is attached to an upper metallic vertical pipe, which can be rotated clockwise and anticlockwise to cause repeated twisting of the stent-graft (<b>B</b>). Distilled water is circulated from the reservoir to the vertical metallic tube through an electronic pulsatile pump. After passing through the stent-graft (lined with an impervious latex membrane), the pressure and volumetric rate of the water flow is regulated and returned to the reservoir. The temperature in the basin is maintained at 37 °C.</p> Full article ">Figure 18
<p>The twist process applied to the stent-grafts. The 35° Z-stent (<b>A1</b>), 45° Z-device (<b>B1</b>) and the ringed device (<b>C1</b>) behave dramatically different. When the gear rotates towards the right, one end of the device is turned anticlockwise (<b>A2</b>,<b>B2</b>,<b>C2</b>) to some twist angle. When the gear rotated towards the left, the devices are returned to their original state (<b>A3</b>,<b>B3</b>,<b>C3</b>) firstly, and then to an anticlockwise twist angle (<b>A4</b>,<b>B4</b>,<b>C4</b>). The Z-stent devices were more severely distorted than the ringed devices, and thus the distilled water flow was more impaired.</p> Full article ">
1188 KiB  
Article
Residual Stress Analysis Based on Acoustic and Optical Methods
by Sanichiro Yoshida, Tomohiro Sasaki, Masaru Usui, Shuichi Sakamoto, David Gurney and Ik-Keun Park
Materials 2016, 9(2), 112; https://doi.org/10.3390/ma9020112 - 16 Feb 2016
Cited by 11 | Viewed by 6384
Abstract
Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able [...] Read more.
Co-application of acoustoelasticity and optical interferometry to residual stress analysis is discussed. The underlying idea is to combine the advantages of both methods. Acoustoelasticity is capable of evaluating a residual stress absolutely but it is a single point measurement. Optical interferometry is able to measure deformation yielding two-dimensional, full-field data, but it is not suitable for absolute evaluation of residual stresses. By theoretically relating the deformation data to residual stresses, and calibrating it with absolute residual stress evaluated at a reference point, it is possible to measure residual stresses quantitatively, nondestructively and two-dimensionally. The feasibility of the idea has been tested with a butt-jointed dissimilar plate specimen. A steel plate 18.5 mm wide, 50 mm long and 3.37 mm thick is braze-jointed to a cemented carbide plate of the same dimension along the 18.5 mm-side. Acoustoelasticity evaluates the elastic modulus at reference points via acoustic velocity measurement. A tensile load is applied to the specimen at a constant pulling rate in a stress range substantially lower than the yield stress. Optical interferometry measures the resulting acceleration field. Based on the theory of harmonic oscillation, the acceleration field is correlated to compressive and tensile residual stresses qualitatively. The acoustic and optical results show reasonable agreement in the compressive and tensile residual stresses, indicating the feasibility of the idea. Full article
(This article belongs to the Special Issue Materials in Motorsport)
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<p>Acoustic sources used in this study. (<b>a</b>) Acoustic transducer. The sensor head was switched between the longitudinal-wave and shear-wave modes for the respective measurements. The grid points indicated on the specimen are the points where the acoustic measurements were made; (<b>b</b>) Point-focused acoustic source for Scanning Acoustic Microscopy. Acoustic frequencies of 400 and 200 MHz were used with the same focusing acoustic lens.</p> Full article ">Figure 2
<p>Spring-mass model to represent residual stresses and external forces.</p> Full article ">Figure 3
<p>Butt-brazed specimen used in the present study.</p> Full article ">Figure 4
<p>Optical arrangement for the electronic speckle-pattern interferometry (ESPI) setup. The illustration is for the <span class="html-italic">x</span> interferometer sensitive to the in-plane displacement component parallel to the tensile axis. An identical configuration for the <span class="html-italic">x</span>-component of the in-plane displacement called the <span class="html-italic">y</span> interferometer was configured. The <span class="html-italic">y</span> interferometer is not illustrated in this figure to avoid complexity. (<b>a</b>) Sample carrier fringe pattern; (<b>b</b>) Sample overall fringe pattern.</p> Full article ">Figure 5
<p>Acoustic velocity in <span class="html-italic">z</span> direction measured with (1) SAM 400 MHz, (2) SAM 200 MHz and (3) contact acoustic transducer.</p> Full article ">Figure 6
<p>Relative acoustic velocity in <span class="html-italic">z</span> direction based on the measurement with the SAM 200 MHz and the contact acoustic transducer.</p> Full article ">Figure 7
<p>Relative acoustic velocity to nominal values for <span class="html-italic">x</span>, <span class="html-italic">y</span> and <span class="html-italic">z</span> direction (the top three rows). The bottom drawings illustrate compressive and tensile residual stresses qualitatively based on the relative acoustic velocity data.</p> Full article ">Figure 8
<p>Residual strain based on relative acoustic velocity on <a href="#materials-09-00112-f007" class="html-fig">Figure 7</a> and Equation (4), and corresponding residual stress evaluated with Equation (6).</p> Full article ">Figure 9
<p>Velocity field 0–200 N (<b>top</b>) and 200–400 N (<b>bottom</b>). In the right figure, the vertical component of velocity is multiplied by a factor of 500 for better visibility of rotational feature.</p> Full article ">Figure 10
<p>Acceleration from electronic speckle-pattern interferometry (ESPI) measurement and acoustic velocity relative to nominal value.</p> Full article ">Figure 11
<p>(<b>a</b>) Strain potential energy. The slope of the potential energy curve represents the stress; (<b>b</b>) The stress as a function of strain. The slope is the elastic modulus.</p> Full article ">Figure 12
<p>Typical <math display="inline"> <mrow> <mi>V</mi> <mo>(</mo> <mi>z</mi> <mo>)</mo> </mrow> </math> curve. Surface acoustic-wave velocity can be obtained from <math display="inline"> <mrow> <mo>Δ</mo> <mi>z</mi> </mrow> </math>.</p> Full article ">
10449 KiB  
Article
An Investigation on the Wear Resistance and Fatigue Behaviour of Ti-6Al-4V Notched Members Coated with Hydroxyapatite Coatings
by Reza H Oskouei, Khosro Fallahnezhad and Sushmitha Kuppusami
Materials 2016, 9(2), 111; https://doi.org/10.3390/ma9020111 - 16 Feb 2016
Cited by 18 | Viewed by 5864
Abstract
In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor [...] Read more.
In this study, surface properties of Ti-6Al-4V alloy coated with hydroxyapatite coatings were investigated. Wear resistance and fatigue behaviour of samples with coating thicknesses of 10 and 50 µm as well as uncoated samples were examined. Wear experiments demonstrated that the friction factor of the uncoated titanium decreased from 0.31 to 0.06, through a fluctuating trend, after 50 cycles of wear tests. However, the friction factor of both the coated samples (10 and 50 µm) gradually decreased from 0.20 to 0.12 after 50 cycles. At the end of the 50th cycle, the penetration depth of the 10 and 50 µm coated samples were 7.69 and 6.06 µm, respectively. Fatigue tests showed that hydroxyapatite coatings could improve fatigue life of a notched Ti-6Al-4V member in both low and high cycle fatigue zones. It was understood, from fractography of the fracture surfaces, that the fatigue zone of the uncoated specimens was generally smaller in comparison with that of the coated specimens. No significant difference was observed between the fatigue life of coated specimens with 10 and 50 µm thicknesses. Full article
(This article belongs to the Special Issue Surface Modification Methods to Improve Fatigue, Fretting Fatigue, and Fretting Wear Behavior of Materials)
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<p>(<b>a</b>) Ti-6Al-4V disc sample coated with hydroxyapatite coatings; (<b>b</b>) fatigue test specimen, dimensions in mm; and (<b>c</b>) notched section of the fatigue test specimen coated with hydroxyapatite coatings.</p> Full article ">Figure 2
<p>(<b>a</b>) Fatigue testing machine, GUNT WP 140; (<b>b</b>) HA coated specimen under fatigue loading; and (<b>c</b>) HA coated specimen after fatigue failure.</p> Full article ">Figure 3
<p>SEM image of: (<b>a</b>) HA coated sample with thickness of 10 µm; (<b>b</b>) HA coated sample with thickness of 50 µm; and (<b>c</b>) uncoated Ti-6Al-4V sample.</p> Full article ">Figure 4
<p>EDS results of hydroxyapatite coatings used in this study.</p> Full article ">Figure 5
<p>3D surface profile of: (<b>a</b>) HA coated sample with thickness of 10 µm; (<b>b</b>) HA coated sample with thickness of 50 µm; and (<b>c</b>) uncoated Ti-6Al-4V sample.</p> Full article ">Figure 6
<p>Wear test results of: (<b>a</b>) friction factor <span class="html-italic">versus</span> number of passes; (<b>b</b>) depth of penetration versus number of passes for three batches of samples.</p> Full article ">Figure 7
<p>S-N curves of uncoated Ti-6Al-4V, 10 µm HA coated and 50 µm HA coated specimens, <span class="html-italic">R</span> = −1.</p> Full article ">Figure 8
<p>SEM images of fatigue fracture surface of uncoated Ti-6Al-4V specimen failed under stress amplitude of 570 MPa and <span class="html-italic">R</span> = −1: (<b>a</b>) fracture surface showing fatigue zones; (<b>b</b>) fatigue crack initiation site A; (<b>c</b>) fatigue crack initiation site B; and (<b>d</b>) higher magnification image of a deep crack in area C.</p> Full article ">Figure 9
<p>SEM images of fatigue fracture surface of 10 µm HA coated specimen failed under stress amplitude of 570 MPa and <span class="html-italic">R</span> = −1: (<b>a</b>) fracture surface showing fatigue zone; (<b>b</b>) fatigue crack initiation site A; (<b>c</b>) higher magnification image of fatigue crack initiation point C; and (<b>d</b>) higher magnification image of fatigue crack initiation site B.</p> Full article ">Figure 9 Cont.
<p>SEM images of fatigue fracture surface of 10 µm HA coated specimen failed under stress amplitude of 570 MPa and <span class="html-italic">R</span> = −1: (<b>a</b>) fracture surface showing fatigue zone; (<b>b</b>) fatigue crack initiation site A; (<b>c</b>) higher magnification image of fatigue crack initiation point C; and (<b>d</b>) higher magnification image of fatigue crack initiation site B.</p> Full article ">Figure 10
<p>SEM images of fatigue fracture surface of 50 µm HA coated specimen failed under stress amplitude of 570 MPa and <span class="html-italic">R</span> = −1: (<b>a</b>) fracture surface showing fatigue zones; (<b>b</b>) fatigue crack initiation site A; (<b>c</b>) fatigue crack initiation site B; and (<b>d</b>) higher magnification image of fatigue crack initiation point C.</p> Full article ">Figure 11
<p>SEM image of the final fracture zone, taken from the 10 µm HA coated specimen.</p> Full article ">
2341 KiB  
Article
Research on the Thermal Decomposition Reaction Kinetics and Mechanism of Pyridinol-Blocked Isophorone Diisocyanate
by Sen Guo, Jingwei He, Weixun Luo and Fang Liu
Materials 2016, 9(2), 110; https://doi.org/10.3390/ma9020110 - 11 Feb 2016
Cited by 17 | Viewed by 6786
Abstract
A series of pyridinol-blocked isophorone isocyanates, based on pyridinol including 2-hydroxypyridine, 3-hydroxypyridine, and 4-hydroxypyridine, was synthesized and characterized by 1H-NMR, 13C-NMR, and FTIR spectra. The deblocking temperature of blocked isocyanates was established by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and [...] Read more.
A series of pyridinol-blocked isophorone isocyanates, based on pyridinol including 2-hydroxypyridine, 3-hydroxypyridine, and 4-hydroxypyridine, was synthesized and characterized by 1H-NMR, 13C-NMR, and FTIR spectra. The deblocking temperature of blocked isocyanates was established by thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and the CO2 evaluation method. The deblocking studies revealed that the deblocking temperature was increased with pyridinol nucleophilicity in this order: 3-hydroxypyridine > 4-hydroxypyridine > 2-hydroxypyridine. The thermal decomposition reaction of 4-hydroxypyridine blocked isophorone diisocyanate was studied by thermo-gravimetric analysis. The Friedman–Reich–Levi (FRL) equation, Flynn–Wall–Ozawa (FWO) equation, and Crane equation were utilized to analyze the thermal decomposition reaction kinetics. The activation energy calculated by FRL method and FWO method was 134.6 kJ·mol−1 and 126.2 kJ·mol−1, respectively. The most probable mechanism function calculated by the FWO method was the Jander equation. The reaction order was not an integer because of the complicated reactions of isocyanate. Full article
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<p>FTIR spectra of blocked isocyanates at different temperatures.</p> Full article ">Figure 2
<p>DSC thermograms of blocked isocyanates.</p> Full article ">Figure 3
<p>TGA-DTG thermograms of blocked isocyanates.</p> Full article ">Figure 4
<p>TGA curves of the blocked isocyanate at different heating rates.</p> Full article ">Figure 5
<p>Fitting curves based on FRL (<b>A</b>) and FWO (<b>B</b>) methods.</p> Full article ">Figure 6
<p>Overall reaction of blocked isocyanates.</p> Full article ">
2792 KiB  
Article
Imaging Techniques and Scanning Electron Microscopy as Tools for Characterizing a Si-Based Material Used in Air Monitoring Applications
by Suárez-Peña Beatriz, Negral Luis, Castrillón Leonor, Megido Laura, Marañón Elena and Fernández-Nava Yolanda
Materials 2016, 9(2), 109; https://doi.org/10.3390/ma9020109 - 11 Feb 2016
Cited by 19 | Viewed by 6511
Abstract
This paper presents a study of the quartz fibrous filters used as a substrate for capturing the particulate matter (PM) present in the air. Although these substrates are widely used in environmental applications, their microstructure has been barely studied. The behavior of these [...] Read more.
This paper presents a study of the quartz fibrous filters used as a substrate for capturing the particulate matter (PM) present in the air. Although these substrates are widely used in environmental applications, their microstructure has been barely studied. The behavior of these devices during the filtration process was investigated in terms of their microstructure and the quartz fibers. Surface and cross sections were monitored. Scanning electronic microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), imaging and stereology techniques were used as tools for this purpose. The results show that most of the quartz filter fibers have sizes that allow them to be classified as nanofibers. It was also observed that, while the mechanisms of the mechanical capture of particles via impaction, interception and diffusion operate simultaneously in the outer zones of the filter cross section, the mechanism of capture by impaction is virtually non-existent in the innermost zones. Particles between 0.1 and 0.5 μm are known to be the most difficult to have captured by means of fibrous substrates. The fibers in inner zones were highly efficient in capturing this type of particle. Full article
(This article belongs to the Special Issue Materials and Nanomaterials for Environmental and Bio-Medical Applications)
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<p>SEM images of a “clean” filter, in which it can be seen that it is made up of quartz fibers of different diameters. (<b>a</b>) Micrograph of the filter surface, in which the existence of points of contact between the quartz fibers can be appreciated; (<b>b</b>) micrograph of the transversal cross section of the filter in which voids can be observed surrounded by groups of quartz fibers, as well as several circumferences of variable radii between the fibers.</p> Full article ">Figure 2
<p>Size distribution of the quartz fibers found in the filters. According to these estimations, 90.714% of quartz fibers can be considered nanofibers.</p> Full article ">Figure 3
<p>Quartz fibrous filter microstructure: (<b>a</b>) Backscattered electron image micrograph of filter surface. Quartz fibers of different diameters and captured particles of different sizes are observed. Those rich in Fe are brighter; (<b>b</b>) Filter cross section taken at a depth of 300 µm. Several particles can be observed deposited on a quartz fiber.</p> Full article ">Figure 4
<p>Backscattered electron image micrographs of the quartz fibrous filter cross section with highlighted zones discussed in more detail in the text. The boxes indicate the selected deposition zones (DZs) and their corresponding microstructure. (<b>a</b>) Deposition in DZ<sub>0</sub>, (<b>b</b>) Deposition in DZ<sub>100</sub>, (<b>c</b>) Deposition in DZ<sub>300</sub>, (<b>d</b>) Deposition in DZ<sub>600</sub>.</p> Full article ">Figure 5
<p>Quantitative determinations of the volume fraction, <span class="html-italic">Vv</span>, for PM10 particles conducted in selected zones of the cross section of the quartz filter. Error bars represent the 95% confidence limit of the determinations.</p> Full article ">Figure 6
<p>Particle size distribution for PM10 particles in selected zones of the cross section of the quartz filter: (<b>a</b>) on the free filter surface, DZ<sub>0</sub>; (<b>b</b>) at a depth of 100 µm, DZ<sub>100</sub>; (<b>c</b>) at a depth of 300 µm, DZ<sub>300</sub>; and (<b>d</b>) at a depth of 600 µm, DZ<sub>600</sub>.</p> Full article ">
3606 KiB  
Article
In-Plane Behaviour of a Reinforcement Concrete Frame with a Dry Stack Masonry Panel
by Kun Lin, Yuri Zarevich Totoev, Hongjun Liu and Tianyou Guo
Materials 2016, 9(2), 108; https://doi.org/10.3390/ma9020108 - 11 Feb 2016
Cited by 23 | Viewed by 5787
Abstract
In order to improve the energy dissipation of the masonry infilled frame structure while decreasing the stiffening and strengthening effects of the infill panels, a new dry stacked panel (DSP) semi-interlocking masonry (SIM) infill panel has been developed. In this paper, the material [...] Read more.
In order to improve the energy dissipation of the masonry infilled frame structure while decreasing the stiffening and strengthening effects of the infill panels, a new dry stacked panel (DSP) semi-interlocking masonry (SIM) infill panel has been developed. In this paper, the material properties of DSP and a traditional unreinforced masonry (URM) panel have been evaluated experimentally. A series of cyclic tests were performed to investigate the cyclic behaviour of the reinforcement concrete (RC) frame with different infill panels. The failure modes, damage evolution, hysteretic behaviour, stiffness degradation and energy dissipation were compared and analysed. We concluded that DSP is capable of significantly improving the seismic energy dissipation due to its hysteretic behaviour when the frame is in elastic stage without increasing the stiffness of the frame. Therefore, DSP or SIM panels can be considered as frictional dampers. Based on the experimental results, the influence of DSP was examined. Using the parallel model, the hysteretic loops of DSP subjected to different load cases were achieved. The typical full hysteretic loop for DSP could be divided into three distinct stages of behaviour: packing stage, constant friction stage and equivalent strut stage. The connection between the panel and the frame had a great effect on the transferring of different mechanical stages. The constant friction stage was verified to provide substantial energy dissipation and benefits to the ductility of the structure, which, therefore, is suggested to be prolonged in reality. Full article
(This article belongs to the Section Advanced Materials Characterization)
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<p>Semi-interlocking masonry units: (<b>a</b>) Rectangular interlocking; (<b>b</b>) Circular interlocking.</p> Full article ">Figure 2
<p>The dimensions of solid concrete bricks.</p> Full article ">Figure 3
<p>Compression-shear test of dry stacked masonry triplets: (<b>a</b>) Schematic diagram of the test; (<b>b</b>) Test setup; (<b>c</b>) Typical test result. LVDT, linear variable displacement transducer.</p> Full article ">Figure 4
<p>Frame details: (<b>a</b>) Instrumentation of frame (unit: mm); (<b>b</b>) Section details. S, strain gage.</p> Full article ">Figure 5
<p>Experimental setup: (<b>a</b>) Test setup (unit: mm); (<b>b</b>) Photos. L, LVDT.</p> Full article ">Figure 6
<p>Displacement history.</p> Full article ">Figure 7
<p>Final crack patterns: (<b>a</b>) Reinforcement concrete frame with the dry stacked panel (DSP); (<b>b</b>) RC frame with the traditional masonry panel (TMP).</p> Full article ">Figure 8
<p>Hysteretic loop of the frame with different infilled forms: (<b>a</b>) Bare frame; (<b>b</b>) RC frame with DSP; (<b>c</b>) Double check test on the bare frame; (<b>d</b>) RC frame with TMP.</p> Full article ">Figure 9
<p>Envelope curves.</p> Full article ">Figure 10
<p>Response mechanisms: (<b>a</b>) Constant friction stage; (<b>b</b>) Equivalent frictional strut stage; (<b>c</b>) Plastic stage.</p> Full article ">Figure 11
<p>Parallel model approach.</p> Full article ">Figure 12
<p>Hysteretic loops for dry stacked panel at different levels of cycling displacement: (<b>a</b>) Load Case 1; (<b>b</b>) Load Case 2; (<b>c</b>) Load Case 3; (<b>d</b>) Load Case 4; (<b>e</b>) Load Case 5; (<b>f</b>) Load Case 6; (<b>g</b>) Load Case 7; (<b>h</b>) Load Case 8; (<b>i</b>) Load Case 9.</p> Full article ">Figure 12 Cont.
<p>Hysteretic loops for dry stacked panel at different levels of cycling displacement: (<b>a</b>) Load Case 1; (<b>b</b>) Load Case 2; (<b>c</b>) Load Case 3; (<b>d</b>) Load Case 4; (<b>e</b>) Load Case 5; (<b>f</b>) Load Case 6; (<b>g</b>) Load Case 7; (<b>h</b>) Load Case 8; (<b>i</b>) Load Case 9.</p> Full article ">Figure 13
<p>Modelling of a typical hysteretic loop for dry stack infill panel: (<b>a</b>) Full hysteretic loop for DSP; (<b>b</b>) Constant friction stage; (<b>c</b>) Equivalent strut stage</p> Full article ">
3348 KiB  
Article
Synthesis, Characterization, Antimicrobial Studies and Corrosion Inhibition Potential of 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane: Experimental and Quantum Chemical Studies
by Henry U. Nwankwo, Collins N. Ateba, Lukman O. Olasunkanmi, Abolanle S. Adekunle, David A. Isabirye, Damian C. Onwudiwe and Eno E. Ebenso
Materials 2016, 9(2), 107; https://doi.org/10.3390/ma9020107 - 11 Feb 2016
Cited by 25 | Viewed by 6746
Abstract
The macrocylic ligand, 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane (MHACD) was synthesized by the demetallation of its freshly synthesized Ni(II) complex (NiMHACD). Successful synthesis of NiMHACD and the free ligand (MHACD) was confirmed by various characterization techniques, including Fourier transform infra-red (FT-IR), proton nuclear magnetic resonance (1 [...] Read more.
The macrocylic ligand, 1,8-dimethyl-1,3,6,8,10,13-hexaazacyclotetradecane (MHACD) was synthesized by the demetallation of its freshly synthesized Ni(II) complex (NiMHACD). Successful synthesis of NiMHACD and the free ligand (MHACD) was confirmed by various characterization techniques, including Fourier transform infra-red (FT-IR), proton nuclear magnetic resonance (1H-NMR), carbon-13 nuclear magnetic resonance (13C-NMR), ultraviolet-visible (UV-vis), and energy dispersive x-ray (EDX) spectroscopic techniques. The anti-bacteria activities of MHACD were investigated against Staphylococcus aureus and Enterococcus species and the results showed that MHACD possesses a spectrum of activity against the two bacteria. The electrochemical cyclic voltammetry study on MHACD revealed that it is a redox active compound with promising catalytic properties in electrochemical applications. The inhibition potential of MHACD for mild steel corrosion in 1 M HCl was investigated using potentiodynamic polarization method. The results showed that MHACD inhibits steel corrosion as a mixed-type inhibitor, and the inhibition efficiency increases with increasing concentration of MHACD. The adsorption of MHACD obeys the Langmuir adsorption isotherm; it is spontaneous and involves competitive physisorption and chemisorption mechanisms. Quantum chemical calculations revealed that the energy of the highest occupied molecular orbital (HOMO) of MHACD is high enough to favor forward donation of charges to the metal during adsorption and corrosion inhibition. Natural bond orbital (NBO) analysis revealed the presence of various orbitals in the MHACD that are capable of donating or accepting electrons under favorable conditions. Full article
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<p>The UV-Vis absorption spectra of NiMHACD and MHACD.</p> Full article ">Figure 2
<p>Antibacterial activities of MHACD against <span class="html-italic">Staphylococcus aureus</span> and <span class="html-italic">Enterococcus</span> species as (<b>a</b>) zone of inhibition against <span class="html-italic">Enterococcus</span> species (A = 4; B = 1; C = 2; D = 3 µg/mL; and the control is the unlabeled white spot at the center of the disc); and (<b>b</b>) variation of inhibition diameter against concentration of MHACD.</p> Full article ">Figure 3
<p>Cyclic voltammograms for bare Pt electrode in 0.1 M PBS (pH 7.0) without and with 1 mM of MHACD at 25 mV·s<sup>−1</sup> scan rate showing the relatively more: (<b>a</b>) cathodic potential region and (<b>b</b>) anodic potential region.</p> Full article ">Figure 4
<p>Effect of scan rate on the electrochemical behavior of MHACD at ν = 25–300 mV·s<sup>−1</sup>.</p> Full article ">Figure 5
<p>Plots of (<b>a</b>) log Ip <span class="html-italic">vs.</span> log ν and (<b>b</b>) E<sub>p</sub> <span class="html-italic">vs.</span> log ν for MHACD.</p> Full article ">Figure 6
<p>Potentiodynamic polarization curves for MS in 1 M HCl without and with various concentrations of the inhibitor (MHACD).</p> Full article ">Figure 7
<p>Langmuir adsorption isotherm for MS in 1 M HCl containing various concentrations of MHACD at 303 K. The values of K<sub>ads</sub> and ΔG<sub>ads</sub> are listed on the graph.</p> Full article ">Figure 8
<p>Optimized structure (<b>a</b>); the highest occupied molecular orbital (HOMO) (<b>b</b>); and and lowest unoccupied molecular orbital (LUMO) (<b>c</b>) of MHACD. Only the non-hydrogen atoms are shown and numbered in the optimized structure such that: grey = Carbon; blue = Nitrogen. The numbering pattern in the optimized structure is used for discussion of the results.</p> Full article ">Figure 9
<p>Synthesis of (NiMHACD).</p> Full article ">Figure 10
<p>Demetallation of NiMHACD to obtain the metal-free ligand, MHACD.</p> Full article ">
6408 KiB  
Article
Fatigue of Ti6Al4V Structural Health Monitoring Systems Produced by Selective Laser Melting
by Maria Strantza, Reza Vafadari, Dieter De Baere, Bey Vrancken, Wim Van Paepegem, Isabelle Vandendael, Herman Terryn, Patrick Guillaume and Danny Van Hemelrijck
Materials 2016, 9(2), 106; https://doi.org/10.3390/ma9020106 - 11 Feb 2016
Cited by 28 | Viewed by 8244
Abstract
Selective laser melting (SLM) is an additive manufacturing (AM) process which is used for producing metallic components. Currently, the integrity of components produced by SLM is in need of improvement due to residual stresses and unknown fracture behavior. Titanium alloys produced by AM [...] Read more.
Selective laser melting (SLM) is an additive manufacturing (AM) process which is used for producing metallic components. Currently, the integrity of components produced by SLM is in need of improvement due to residual stresses and unknown fracture behavior. Titanium alloys produced by AM are capable candidates for applications in aerospace and industrial fields due to their fracture resistance, fatigue behavior and corrosion resistance. On the other hand, structural health monitoring (SHM) system technologies are promising and requested from the industry. SHM systems can monitor the integrity of a structure and during the last decades the research has primarily been influenced by bionic engineering. In that aspect a new philosophy for SHM has been developed: the so-called effective structural health monitoring (eSHM) system. The current system uses the design freedom provided by AM. The working principle of the system is based on crack detection by means of a network of capillaries that are integrated in a structure. The main objective of this research is to evaluate the functionality of Ti6Al4V produced by the SLM process in the novel SHM system and to confirm that the eSHM system can successfully detect cracks in SLM components. In this study four-point bending fatigue tests on Ti6Al4V SLM specimens with an integrated SHM system were conducted. Fractographic analysis was performed after the final failure, while finite element simulations were used in order to determine the stress distribution in the capillary region and on the component. It was proven that the SHM system does not influence the crack initiation behavior during fatigue. The results highlight the effectiveness of the eSHM on SLM components, which can potentially be used by industrial and aerospace applications. Full article
(This article belongs to the Special Issue Failure Analysis in Materials)
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<p>Four-point bending specimen’s dimensions (mm): 2D side and front views.</p> Full article ">Figure 2
<p>Schematic of four-point bending setup with the specimen and the installed pressure sensor.</p> Full article ">Figure 3
<p>Maximum stress <span class="html-italic">vs.</span> specimen numbers for the conventional and SLM Ti6Al4V specimens in as-built (AB) and stress relieved (SR) conditions.</p> Full article ">Figure 4
<p>Pressure <span class="html-italic">vs.</span> elapsed time for (<b>a</b>) Specimen 3; and (<b>b</b>) Specimen 5 produced by SLM during the last second of the fatigue test.</p> Full article ">Figure 5
<p>SEM micrographs of a fracture surface of Specimen 6 with maximum stress of 620 MPa. The fracture surface is shown in (<b>a</b>) and the capillary region is shown in (<b>b</b>) in high magnification; (<b>c</b>,<b>d</b>,<b>e</b>) depict the corresponding crack initiation point, while (<b>f</b>) shows the fast fracture region.</p> Full article ">Figure 6
<p>Fracture surface of Specimen 5 with maximum stress of 537 MPa. The fracture surface is shown in (<b>a</b>) and the defect is visible in (<b>b</b>); the capillary region is depicted in (<b>c</b>) in high magnification, while (<b>d</b>) shows un-molten powder particles concentrated around the capillary.</p> Full article ">Figure 7
<p>Fracture surface of Specimen 3 with maximum stress of 323 MPa. The defect is shown in (<b>a</b>), a close-up of the defect in (<b>b</b>,<b>c</b>) while a part of the fracture surface with gas inclusions is depicted in (<b>d</b>).</p> Full article ">Figure 8
<p>Micrographs of the macrostructure of (<b>a</b>) side view parallel to the building direction (BD) of Ti6Al4V SLM Specimen 3; (<b>b</b>) top view perpendicular to the BD of Ti6Al4V SLM Specimen 3 and (<b>c</b>) top view of the Ti6Al4V conventional specimen.</p> Full article ">Figure 9
<p>Schematic description of the paths used for extracting stresses in the numerical simulations.</p> Full article ">Figure 10
<p>Comparing the stress distributions for a load of 20 kN for the capillary structure with (<b>a</b>) a period of 20 mm (Specimens 1, 2, 3, 4 and stress relieved (SR));and (<b>b</b>) a period of 22.4 mm (Specimens 5 and 6).</p> Full article ">
11620 KiB  
Article
Increased Durability of Concrete Made with Fine Recycled Concrete Aggregates Using Superplasticizers
by Francisco Cartuxo, Jorge De Brito, Luis Evangelista, José Ramón Jiménez and Enrique F. Ledesma
Materials 2016, 9(2), 98; https://doi.org/10.3390/ma9020098 - 8 Feb 2016
Cited by 84 | Viewed by 7649
Abstract
This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made [...] Read more.
This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made with a high-performance superplasticizer. Five volumetric replacement ratios of natural sand by FRCA were tested: 0%, 10%, 30%, 50% and 100%. Two natural gravels were used as coarse aggregates. All mixes had the same particle size distribution, cement content and amount of superplasticizer. The w/c ratio was calibrated to obtain similar slump. The results showed that the incorporation of FRCA increased the water absorption by immersion, the water absorption by capillary action, the carbonation depth and the chloride migration coefficient, while the use of superplasticizers highly improved these properties. The incorporation of FRCA jeopardized the SP’s effectiveness. This research demonstrated that, from a durability point of view, the simultaneous incorporation of FRCA and high-performance SP is a viable sustainable solution for structural concrete production. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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Graphical abstract
Full article ">Figure 1
<p>Particle size distribution of the natural aggregate (NA), and fine recycled concrete aggregate (FRCA) and FAURY curve.</p> Full article ">Figure 2
<p>Carbonation resistance test.</p> Full article ">Figure 3
<p>Equipment to measure chloride penetration.</p> Full article ">Figure 4
<p>Water absorption by immersion.</p> Full article ">Figure 5
<p>Influence of FRCA replacement ratio on the relative water absorption by immersion.</p> Full article ">Figure 6
<p>Water absorption by immersion <span class="html-italic">vs.</span> effective w/c ratio.</p> Full article ">Figure 7
<p>Water absorption by immersion <span class="html-italic">vs.</span> 28-day compressive strength.</p> Full article ">Figure 8
<p>Capillary water absorption over time—concrete family C0 (without SP).</p> Full article ">Figure 9
<p>Capillary water absorption over time—concrete family C1 (with SP1).</p> Full article ">Figure 10
<p>Capillary water absorption over time—concrete family C2 (with SP2).</p> Full article ">Figure 11
<p>Capillary water absorption.</p> Full article ">Figure 12
<p>Influence of FRCA replacement ratio on the relative capillary water absorption.</p> Full article ">Figure 13
<p>Capillary water absorption by immersion <span class="html-italic">vs.</span> water absorption by immersion.</p> Full article ">Figure 14
<p>Carbonation depth at seven days.</p> Full article ">Figure 15
<p>Carbonation depth at 91 days.</p> Full article ">Figure 16
<p>Influence of FRCA replacement ratio on the relative carbonation depth at seven days.</p> Full article ">Figure 17
<p>Influence of FRCA replacement ratio on the relative carbonation depth at 91 days.</p> Full article ">Figure 18
<p>Carbonation depth <span class="html-italic">vs.</span> effective w/c ratio.</p> Full article ">Figure 19
<p>Carbonation depth <span class="html-italic">vs.</span> compressive strength.</p> Full article ">Figure 20
<p>Chloride diffusion coefficient at 91 days.</p> Full article ">Figure 21
<p>Influence of FRCA replacement ratio on the relative chloride diffusion coefficient at 91 days.</p> Full article ">Figure 22
<p>Chloride diffusion coefficient at 91 days <span class="html-italic">vs.</span> effective w/c ratio.</p> Full article ">Figure 23
<p>Chloride diffusion coefficient at 91 days <span class="html-italic">vs.</span> compressive strength.</p> Full article ">
1833 KiB  
Article
Investigation of Pozzolanic Reaction in Nanosilica-Cement Blended Pastes Based on Solid-State Kinetic Models and 29Si MAS NMR
by Jiho Moon, Mahmoud M. Reda Taha, Kwang-Soo Youm and Jung J. Kim
Materials 2016, 9(2), 99; https://doi.org/10.3390/ma9020099 - 6 Feb 2016
Cited by 37 | Viewed by 7016
Abstract
The incorporation of pozzolanic materials in concrete has many beneficial effects to enhance the mechanical properties of concrete. The calcium silicate hydrates in cement matrix of concrete increase by pozzolanic reaction of silicates and calcium hydroxide. The fine pozzolanic particles fill spaces between [...] Read more.
The incorporation of pozzolanic materials in concrete has many beneficial effects to enhance the mechanical properties of concrete. The calcium silicate hydrates in cement matrix of concrete increase by pozzolanic reaction of silicates and calcium hydroxide. The fine pozzolanic particles fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. In this study, Ordinary Portland Cement (OPC) was mixed with 1% and 3% nanosilica by weight to produce cement pastes with water to binder ratio (w/b) of 0.45. The specimens were cured for 7 days. 29Si nuclear magnetic resonance (NMR) experiments are conducted and conversion fraction of nanosilica is extracted. The results are compared with a solid-state kinetic model. It seems that pozzolanic reaction of nanosilica depends on the concentration of calcium hydroxide. Full article
(This article belongs to the Special Issue Utilisation of By-Product Materials in Concrete)
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<p>Schematic representation of one-dimensional diffusion through a flat plane.</p> Full article ">Figure 2
<p>Schematic representation of radial diffusion in a sphere.</p> Full article ">Figure 3
<p>Silicate connections detected from the analysis of <sup>29</sup>Si magic angle spinning nuclear magnetic resonance (MAS NMR) spectra.</p> Full article ">Figure 4
<p>Schematic representation of silicate polymerization.</p> Full article ">Figure 5
<p>Full reaction time of silicate particles according to particle diameters ranging to (<b>a</b>) 120 μm and (<b>b</b>) 120 nm, JD model and GB model represent Jander’s model in Equation (1) and Ginstling-Broushtein model in Equation (3) respectively.</p> Full article ">Figure 6
<p>NMR spectra of (<b>a</b>) 0; (<b>b</b>) 1%; and (<b>c</b>) 3% nanosilica (black, red, and dotted lines as spectrum from NMR experiments, total spectrum by summing all Q spectra, and each Q spectrum, respectively).</p> Full article ">Figure 6 Cont.
<p>NMR spectra of (<b>a</b>) 0; (<b>b</b>) 1%; and (<b>c</b>) 3% nanosilica (black, red, and dotted lines as spectrum from NMR experiments, total spectrum by summing all Q spectra, and each Q spectrum, respectively).</p> Full article ">
2366 KiB  
Article
Bone Regeneration Using a Mixture of Silicon-Substituted Coral HA and β-TCP in a Rat Calvarial Bone Defect Model
by Jiyeon Roh, Ji-Youn Kim, Young-Muk Choi, Seong-Min Ha, Kyoung-Nam Kim and Kwang-Mahn Kim
Materials 2016, 9(2), 97; https://doi.org/10.3390/ma9020097 - 6 Feb 2016
Cited by 14 | Viewed by 5673
Abstract
The demand of bone graft materials has been increasing. Among various origins of bone graft materials, natural coral composed of up to 99% calcium carbonate was chosen and converted into hydroxyapatite (HA); silicon was then substituted into the HA. Then, the Si-HA was [...] Read more.
The demand of bone graft materials has been increasing. Among various origins of bone graft materials, natural coral composed of up to 99% calcium carbonate was chosen and converted into hydroxyapatite (HA); silicon was then substituted into the HA. Then, the Si-HA was mixed with β-tricalcium phosphate (TCP) in the ratios 100:0 (S100T0), 70:30 (S70T30), 60:40 (S60T40), and 50:50 (S50T50). The materials were implanted for four and eight weeks in a rat calvarial bone defect model (8 mm). The MBCPTM (HA:β-TCP = 60:40, Biomatalante, Vigneux de Bretagne, France) was used as a control. After euthanasia, the bone tissue was analyzed by making histological slides. From the results, S60T40 showed the fastest bone regeneration in four weeks (p < 0.05). In addition, S60T40, S50T50, and MBCPTM showed significant new bone formation in eight weeks (p < 0.05). In conclusion, Si-HA/TCP showed potential as a bone graft material. Full article
(This article belongs to the Section Biomaterials)
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Full article ">Figure 1
<p>X-ray pictures (four weeks and eight weeks); Cont is the blank control group.</p> Full article ">Figure 2
<p>Histological slides with Masson’s Trichrome staining (four weeks and eight weeks).</p> Full article ">Figure 3
<p>Quantitative results of new bone formation: (<b>A</b>) four weeks; and (<b>B</b>) eight weeks.<b>*</b>, # means significant differences (<span class="html-italic">p</span> &lt; 0.05).</p> Full article ">Figure 4
<p>The surgical process (8 mm defect criteria).</p> Full article ">
4294 KiB  
Article
Multi-Material Front Contact for 19% Thin Film Solar Cells
by Joop Van Deelen, Yasemin Tezsevin and Marco Barink
Materials 2016, 9(2), 96; https://doi.org/10.3390/ma9020096 - 6 Feb 2016
Cited by 7 | Viewed by 7331
Abstract
The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, [...] Read more.
The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,Ga)Se2 (CIGS), CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO) sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
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Full article ">Figure 1
<p>Schematic representations (not to scale) of different interconnection and cell layouts with a side view (<b>a</b>,<b>c</b>,<b>e</b>,<b>g</b>) and a top view (<b>b</b>,<b>d</b>,<b>f</b>,<b>h</b>). The top image shows the front contact (in green), the absorber material (in blue) and the back contact (in grey). In addition, the separation and interconnection layout between two adjacent cells is shown. The surface area of the TCO/back contact material interface is indicated by the white dashed box. The flow of current is depicted by the arrows. The second highest image shows the case where the front contact is supplemented by a metal grid (in orange), whereas the right image displays the area covered by the metal (not to scale). The third image shows the case of the metal interconnect, for which two material interfaces are important: the metal back contact area represented by the white dashed box and the metal/TCO contact areas represented by the blue dashed box.</p> Full article ">Figure 2
<p>I-V characteristics used for the study (<b>a</b>) cells of 19% efficiency with different open circuit voltages (in V, see legend); and (<b>b</b>) cell with a Voc of 0.7 V for different light intensities (see legend) in which one sun is equivalent to 1000 W/m<sup>2</sup>).</p> Full article ">Figure 3
<p>Transmittance as a function of the sheet resistance. This is used to represent TCO induced optical losses in industrially sputtered ZnO: Al material for a wavelength between 400 nm and 1100 nm and do not reflect state of the art laboratory results.</p> Full article ">Figure 4
<p>Efficiency of solar panels as a function of the individual cell length for different sheet resistances of the TCO (Rsh in Ω/sq) for a scribe width of 150 µm (<b>a</b>) and 350 µm (<b>b</b>). The cell was based on a Voc of 0.7 V.</p> Full article ">Figure 5
<p>Efficiency of solar panels as a function of the individual cell length for different open circuit voltages (Voc in V) for a scribe width of 150 µm (<b>a</b>) and 350 µm (<b>b</b>). The front contact consists of a TCO of 10 Ω/sq.</p> Full article ">Figure 6
<p>Efficiency of solar panels as function of the individual cell length for TCO-plus-grid front contact with different finger heights (H<sub>F</sub>, in µm) for a scribe width of 150 µm (<b>a</b>) and 350 µm (<b>b</b>). The cell was based on a Voc of 0.7 V and the finger width is 20 µm. The TCO in the legend refers to calculations with a cell with a TCO of 10 Ω/sq.</p> Full article ">Figure 7
<p>Efficiency of solar panels as a function of the individual cell length for different grid finger heights (H<sub>F</sub>, in µm) for a scribe width of 150 µm (<b>a</b>,<b>c</b>) and 350 µm (<b>b</b>,<b>d</b>). The finger width is 60 µm (<b>a</b>,<b>b</b>) and 100 µm (<b>c</b>,<b>d</b>). The data are based on a Voc of 0.7 V.</p> Full article ">Figure 8
<p>Contact resistance for a 1 cm<sup>2</sup> cell as a function of the width of the contact area between the TCO and the Mo (<b>a</b>) and the metal busbar and the TCO (<b>b</b>). The legend shows the specific contact resistance (R<sub>scr</sub>, in Ω cm<sup>2</sup>). The cell length is 5 mm.</p> Full article ">Figure 9
<p>Contact resistance for a cell of 1 cm<sup>2</sup> for a cell with metal interconnect and fingers as a function of the finger width for various specific contact resistances (R<sub>scr</sub>, in Ω cm<sup>2</sup>). Ω 2.5. Impact of Contact Resistance on Cell Performance.</p> Full article ">Figure 10
<p>Efficiency as a function of the cell length and specific contact resistance for cells with 150 µm (<b>a</b>) and 350 µm (<b>b</b>) scribe width.</p> Full article ">Figure 11
<p>Efficiency as a function of the cell length for various specific contact resistances (see legend, R<sub>scr</sub>, in Ω cm<sup>2</sup>), and TCO (without contact resistance) for cells with finger grid width of 20 µm (<b>a</b>,<b>c</b>,<b>e</b>) and 60 µm (<b>b</b>,<b>d</b>,<b>f</b>) and a height of 2 µm (<b>a</b>,<b>b</b>), 5 µm (<b>c</b>,<b>d</b>) and 50 µm (<b>e</b>,<b>f</b>). Calculations were based on a 19% small cell.</p> Full article ">Figure 12
<p>Efficiency as function of the cell length for different light intensities (see legend in sun units, whereby one sun is 1000 W/m<sup>2</sup>): (<b>a</b>) calculated values; (<b>b</b>) normalized values.</p> Full article ">Figure 13
<p>Efficiency as function of the cell length for various specific contact resistances (R<sub>scr</sub>, in Ohm cm<sup>2</sup>) for light intensity of: 0.2 sun (<b>a</b>); 0.5 sun (<b>b</b>); 0.75 sun (<b>c</b>); and 1 sun (<b>d</b>).</p> Full article ">
2715 KiB  
Review
Irradiation Induced Microstructure Evolution in Nanostructured Materials: A Review
by Wenbo Liu, Yanzhou Ji, Pengkang Tan, Hang Zang, Chaohui He, Di Yun, Chi Zhang and Zhigang Yang
Materials 2016, 9(2), 105; https://doi.org/10.3390/ma9020105 - 6 Feb 2016
Cited by 45 | Viewed by 7921
Abstract
Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void [...] Read more.
Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs) and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials) which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments. Full article
(This article belongs to the Special Issue Nuclear Materials 2015)
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<p>Morphology of void denuded zones (VDZs) along grain boundaries (GBs) in (<b>a</b>) copper irradiated at 330 °C [<a href="#B14-materials-09-00105" class="html-bibr">14</a>]; (<b>b</b>) 304 stainless steel irradiated at 625 °C [<a href="#B17-materials-09-00105" class="html-bibr">17</a>]; (<b>c</b>) nickel irradiated at high temperature [<a href="#B12-materials-09-00105" class="html-bibr">12</a>]; and (<b>d</b>) PNC316CW stainless steel neutron-irradiated at 775 K to 103 dpa [<a href="#B16-materials-09-00105" class="html-bibr">16</a>].</p> Full article ">Figure 2
<p>Schematic descriptions for the free energy of point defects (ΔG<sub>pd</sub>), grain boundaries (ΔG<sub>gb</sub>) and phase-transition (ΔG<sub>pt</sub>) in irradiated nanostructured materials as a function of grain size (d) [<a href="#B38-materials-09-00105" class="html-bibr">38</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) Irradiation-induced voids in Cu layers in irradiated accumulative roll bonding (ARB) nanolayered (NL) Cu-Nb composites with individual layer thickness of 135 nm; (<b>b</b>) illustration of the method to determine the void number density in Cu layers; and (<b>c</b>) plot of the number density of voids as a function of distance from the center of the layer in 133 nm-, 30 nm-, and 15 nm-thick Cu layers [<a href="#B47-materials-09-00105" class="html-bibr">47</a>].</p> Full article ">Figure 4
<p>Sequence of dark-field TEM images and associated electron-diffraction patterns showing the effects of Xe-ion irradiation on nanocrystalline ZrO<sub>2</sub>. The number in the bottom right corner of each diffraction pattern is the ion dose in dpa. The dark-field images were taken with the objective aperture centered over the bright (111) diffraction ring [<a href="#B67-materials-09-00105" class="html-bibr">67</a>].</p> Full article ">Figure 5
<p>Sequence of bright-field TEM images taken at different ion doses showing grain-growth induced by ion irradiation at room temperature; from top to bottom: pure Au thin-film irradiated with 500 keV Ar ions, Ptthin-film irradiated with 500 keV Ar ions, and Cu thin-film irradiated with 500 keV Kr ions [<a href="#B81-materials-09-00105" class="html-bibr">81</a>]. The scale mark is 50 nm.</p> Full article ">Figure 6
<p>Average grain size <span class="html-italic">versus</span> ion fluence for pure Zr and Zr-1.2%Fe irradiated with 500 keV Kr ions at 20 K [<a href="#B80-materials-09-00105" class="html-bibr">80</a>].</p> Full article ">
1284 KiB  
Article
Effect of Addition of Colloidal Silica to Films of Polyimide, Polyvinylpyridine, Polystyrene, and Polymethylmethacrylate Nano-Composites
by Soliman Abdalla, Fahad Al-Marzouki, Abdullah Obaid and Salah Gamal
Materials 2016, 9(2), 104; https://doi.org/10.3390/ma9020104 - 6 Feb 2016
Cited by 9 | Viewed by 4772
Abstract
Nano-composite films have been the subject of extensive work for developing the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nanoparticle size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that forms the insulating film between the [...] Read more.
Nano-composite films have been the subject of extensive work for developing the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nanoparticle size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that forms the insulating film between the conductive electrodes of a capacitor. This in turn affects the energy storage performance of the capacitor. In the present work, we have studied the dielectric properties of four highly pure amorphous polymer films: polymethyl methacrylate (PMMA), polystyrene, polyimide and poly-4-vinylpyridine. Comparison between the dielectric properties of these polymers has revealed that the higher breakdown performance is a character of polyimide (PI) and PMMA. Also, our experimental data shows that adding colloidal silica to PMMA and PI leads to a net decrease in the dielectric properties compared to the pure polymer. Full article
(This article belongs to the Section Advanced Composites)
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<p>TEM illustrations of polymer nano-composite polystyrene films at different silica loading: (<b>a</b>) 1%; (<b>b</b>) 5%; (<b>c</b>) 7.5%; and (<b>d</b>) 15%.</p> Full article ">Figure 2
<p>(<b>a</b>) The dielectric constant ε as a function of silica content for PS, P4VP, PI and PMMA; (<b>b</b>) The electrical conductivity σ as a function of silica content for PS, P4VP, PI and PMMA.</p> Full article ">Figure 3
<p>The probability of failure (P%) as a function of silica content for PS, P4VP, PI and PMMA.</p> Full article ">Figure 4
<p>The breakdown strength (EBD) as a function of silica content for PS, P4VP, PI and PMMA.</p> Full article ">Figure 5
<p>The shape parameter (β) as a function of silica content for PS, P4VP, PI and PMMA.</p> Full article ">
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Article
Dual Function Behavior of Carbon Fiber-Reinforced Polymer in Simulated Pore Solution
by Ji-Hua Zhu, Guanping Guo, Liangliang Wei, Miaochang Zhu and Xianchuan Chen
Materials 2016, 9(2), 103; https://doi.org/10.3390/ma9020103 - 6 Feb 2016
Cited by 21 | Viewed by 5759
Abstract
The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP) were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection [...] Read more.
The mechanical and electrochemical performance of carbon fiber-reinforced polymer (CFRP) were investigated regarding a novel improvement in the load-carrying capacity and durability of reinforced concrete structures by adopting CFRP as both a structural strengthener and an anode of the impressed current cathodic protection (ICCP) system. The mechanical and anode performance of CFRP were investigated in an aqueous pore solution in which the electrolytes were available to the anode in a cured concrete structure. Accelerated polarization tests were designed with different test durations and various levels of applied currents in accordance with the international standard. The CFRP specimens were mechanically characterized after polarization. The measured feeding voltage and potential during the test period indicates CFRP have stable anode performance in a simulated pore solution. Two failure modes were observed through tensile testing. The tensile properties of the post-polarization CFRP specimens declined with an increased charge density. The CFRP demonstrated success as a structural strengthener and ICCP anode. We propose a mathematic model predicting the tensile strengths of CFRP with varied impressed charge densities. Full article
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<p>Geometric dimensions of carbon fiber-reinforced polymer (CFRP) specimens. (<b>a</b>) Front view; (<b>b</b>) Sectional view (unit: mm).</p> Full article ">Figure 2
<p>Schematic view of the simulated impressed current cathodic protection (ICCP) system.</p> Full article ">Figure 3
<p>The feeding voltage between CFRP and stainless steel during galvanostatic anodic polarization process.</p> Full article ">Figure 4
<p>The potential (<span class="html-italic">vs.</span> SCE) of CFRP during galvanostatic anodic polarization process.</p> Full article ">Figure 5
<p>Failure modes of CFRP specimens obtained from tensile tests. (<b>a</b>) L (Lateral) failure mode; (<b>b</b>) D (edge Delamination) failure mode, front surface; (<b>c</b>) D (edge Delamination) failure mode, back surface; and (<b>d</b>) D (edge Delamination) failure mode, side view.</p> Full article ">Figure 6
<p>The relationship between tensile strength, K and charge density for CFRP specimens with pore solution subjected to anodic polarization.</p> Full article ">Figure 7
<p>An eight-steel rebar-reinforced concrete element wrapped with CFRP plate as an anode.</p> Full article ">
3541 KiB  
Article
Long-Term Progressive Degradation of the Biological Capability of Titanium
by Hajime Minamikawa, Wael Att, Takayuki Ikeda, Makoto Hirota and Takahiro Ogawa
Materials 2016, 9(2), 102; https://doi.org/10.3390/ma9020102 - 6 Feb 2016
Cited by 32 | Viewed by 4551
Abstract
Titanium undergoes time-dependent degradation in biological capability, or “biological aging”. It is unknown whether the biological aging of titanium occurs beyond four weeks and whether age-related changes are definitely associated with surface hydrophilicity. We therefore measured multiple biological parameters of bone marrow-derived osteoblasts [...] Read more.
Titanium undergoes time-dependent degradation in biological capability, or “biological aging”. It is unknown whether the biological aging of titanium occurs beyond four weeks and whether age-related changes are definitely associated with surface hydrophilicity. We therefore measured multiple biological parameters of bone marrow-derived osteoblasts cultured on newly prepared, one-month-old, three-month-old, and six-month-old acid-etched titanium surfaces, as well as the hydrophilicity of these surfaces. New surfaces were superhydrophilic with a contact angle of ddH2O of 0°, whereas old surfaces were all hydrophobic with the contact angle of around 90°. Cell attachment, cell spread, cell density, and alkaline phosphatase activity were highest on new surfaces and decreased in a time-dependent manner. These decreases persisted and remained significant for most of the biological parameters up to six-months. While the number of attached cells was negatively correlated with hydrophilicity, the other measured parameters were not. The biological capability of titanium continues to degrade up to six months of aging, but these effects are not directly associated with time-dependent reductions in hydrophilicity. A full understanding of the biological aging will help guide regulatory improvements in implant device manufacturing and develop countermeasures against this phenomenon in order to improve clinical outcomes. Full article
(This article belongs to the Section Biomaterials)
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<p>Scanning electron microscopic (SEM) images of new titanium samples (<b>A</b>,<b>B</b>) and 6-month-old titanium samples (<b>C</b>,<b>D</b>) in low and high magnifications.</p> Full article ">Figure 1 Cont.
<p>Scanning electron microscopic (SEM) images of new titanium samples (<b>A</b>,<b>B</b>) and 6-month-old titanium samples (<b>C</b>,<b>D</b>) in low and high magnifications.</p> Full article ">Figure 2
<p>Hydrophilic or hydrophobic status of new and differently aged titanium surfaces. Side-view images of 10 μL·ddH<sub>2</sub>O placed on titanium disks along with the measured contact angle. The contact angle on all aged surfaces was significantly greater than that on new surface (<span class="html-italic">p</span> &lt; 0.001), whereas there was no significant difference among the differently aged surfaces.</p> Full article ">Figure 3
<p>The number of osteoblasts attached to new and differently aged titanium surfaces during a 3-h incubation. Representative confocal microscopic images of osteoblast culture on each of the titanium surfaces are also presented. The number of attached cells on aged surfaces (1-month-old, 3-month-old, and 6-month-old surfaces) was all significantly lower than that on new surfaces (<span class="html-italic">p</span> &lt; 0.01). * <span class="html-italic">p</span> &lt; 0.05, statistically significant difference among differently aged surfaces.</p> Full article ">Figure 4
<p>Attachment and spreading behavior of osteoblasts on new and differently aged titanium surfaces. Confocal microscopic images of osteoblast with immunochemical stain for cytoskeletal actin and adhesion protein, vinculin are shown. Cytomorphometric parameters measured from the images are presented at the bottom. All parameters were significantly lower on the aged surfaces (1-month-old, 3-month-old, and 6-month-old surfaces) than on new surfaces (<span class="html-italic">p</span> &lt; 0.05). * <span class="html-italic">p</span> &lt; 0.05, statistically significant difference among differently aged surfaces.</p> Full article ">Figure 5
<p>Cell density measured at day 5 of couture. The cell density was significantly lower on all aged surfaces (1-month-old, 3-month-old, and 6-month-old surfaces) than on new surfaces (<span class="html-italic">p</span> &lt; 0.05). ** <span class="html-italic">p</span> &lt; 0.01, * <span class="html-italic">p</span> &lt; 0.05, statistically significant difference among differently aged surfaces.</p> Full article ">Figure 6
<p>Alkaline phosphatase (ALP) activity at day 5 of culture on new and differently-aged titanium surfaces. The ALP activity was significantly lower on all aged surfaces (1-month-old, 3-month-old, and 6-month-old surfaces) than on new surfaces (<span class="html-italic">p</span> &lt; 0.05). * <span class="html-italic">p</span> &lt; 0.05, statistically significant difference among differently aged surfaces.</p> Full article ">Figure 7
<p>Expression of bone-related genes in osteoblast cultures at days 7 examined by reverse transcriptase-polymerase chain reaction (RT-PCR). Expression levels were quantified relative to the level of GAPDH mRNA expression.</p> Full article ">Figure 8
<p>Plot of biological parameters against the contact angle of ddH<sub>2</sub>O. The number of attached cells at 3 h (<b>A</b>); cell area at 3 h (<b>B</b>) and ALP activity at day 5 (<b>C</b>) plotted in association with the contact angle of ddH<sub>2</sub>O. A significant inverse linear correlation was found only for the number of attached cells.</p> Full article ">
4003 KiB  
Communication
Tungsten as a Chemically-Stable Electrode Material on Ga-Containing Piezoelectric Substrates Langasite and Catangasite for High-Temperature SAW Devices
by Gayatri K. Rane, Marietta Seifert, Siegfried Menzel, Thomas Gemming and Jürgen Eckert
Materials 2016, 9(2), 101; https://doi.org/10.3390/ma9020101 - 6 Feb 2016
Cited by 20 | Viewed by 5259
Abstract
Thin films of tungsten on piezoelectric substrates La3Ga5SiO14 (LGS) and Ca3TaGa3Si2O14 (CTGS) have been investigated as a potential new electrode material for interdigital transducers for surface acoustic wave-based sensor devices operating [...] Read more.
Thin films of tungsten on piezoelectric substrates La3Ga5SiO14 (LGS) and Ca3TaGa3Si2O14 (CTGS) have been investigated as a potential new electrode material for interdigital transducers for surface acoustic wave-based sensor devices operating at high temperatures up to 800 °C under vacuum conditions. Although LGS is considered to be suitable for high-temperature applications, it undergoes chemical and structural transformation upon vacuum annealing due to diffusion of gallium and oxygen. This can alter the device properties depending on the electrode nature, the annealing temperature, and the duration of the application. Our studies present evidence for the chemical stability of W on these substrates against the diffusion of Ga/O from the substrate into the film, even upon annealing up to 800 °C under vacuum conditions using Auger electron spectroscopy and energy-dispersive X-ray spectroscopy, along with local studies using transmission electron microscopy. Additionally, the use of CTGS as a more stable substrate for such applications is indicated. Full article
(This article belongs to the Section Advanced Composites)
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<p>Electrical resistivity upon annealing 100 nm·W films on LGS and CTGS at 400 °C, 600 °C, and 800 °C for 12 h each under vacuum (a maximum error of &lt; 5 % is considered due to fluctuation in the voltage).</p> Full article ">Figure 2
<p>Low magnification SEM images of W films on (<b>a</b>) LGS and (<b>b</b>) CTGS post-annealing at 800 °C for 12 h under vacuum (high-magnification images are shown in the inset).</p> Full article ">Figure 3
<p>AES depth profiles made at (<b>a</b>) non-defected region on W-LGS, (<b>b</b>) around the blister location on W-LGS, and (<b>c</b>) on W-CTGS.</p> Full article ">Figure 4
<p>FIB-cut around the blistered area on W-LGS after annealing to 800 °C showing a grain pushed out.</p> Full article ">Figure 5
<p>TEM images along with the composition (table inset) of the marked regions obtained by EDX analysis of (<b>a</b>) W-LGS; (<b>b</b>) W-LGS showing the blister; and (<b>c</b>) W-CTGS.</p> Full article ">
3876 KiB  
Communication
High Pressure Laminates with Antimicrobial Properties
by Sandra Magina, Mauro D. Santos, João Ferra, Paulo Cruz, Inês Portugal and Dmitry Evtuguin
Materials 2016, 9(2), 100; https://doi.org/10.3390/ma9020100 - 6 Feb 2016
Cited by 12 | Viewed by 8589
Abstract
High-pressure laminates (HPLs) are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB) was incorporated for the first time into melamine-formaldehyde resin (MF) matrix on [...] Read more.
High-pressure laminates (HPLs) are durable, resistant to environmental effects and good cost-benefit decorative surface composite materials with special properties tailored to meet market demand. In the present work, polyhexamethylene biguanide (PHMB) was incorporated for the first time into melamine-formaldehyde resin (MF) matrix on the outer layer of HPLs to provide them antimicrobial properties. Chemical binding of PHMB to resin matrix was detected on the surface of produced HPLs by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Antimicrobial evaluation tests were carried out on the ensuing HPLs doped with PHMB against gram-positive Listeria innocua and gram-negative Escherichia coli bacteria. The results revealed that laminates prepared with 1.0 wt % PHMB in MF resin were bacteriostatic (i.e., inhibited the growth of microorganisms), whereas those prepared with 2.4 wt % PHMB in MF resin exhibited bactericidal activity (i.e., inactivated the inoculated microorganisms). The results herein reported disclose a promising strategy for the production of HPLs with antimicrobial activity without affecting basic intrinsic quality parameters of composite material. Full article
(This article belongs to the Special Issue Self-Cleaning and Antimicrobial Surfaces)
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<p>Typical assembly for a high pressure laminates build-up.</p> Full article ">Figure 2
<p>Chemical structure of poly(hexamethylene biguanide).</p> Full article ">Figure 3
<p>Schematic representation of HPLs containing PHMB: (<b>a</b>) decorative paper impregnation strategies; (<b>b</b>) build-up approaches for HPLs without PHMB (SS and SSS) and with PHMB (AS and SAS).</p> Full article ">Figure 4
<p>ATR-FTIR spectra of standard HPL and PHMB-HPL (2.4%(IN) SAS).</p> Full article ">Figure 5
<p>Antimicrobial activity of DPL towards <span class="html-italic">E. coli</span> and <span class="html-italic"> L. innocua</span>, immediately after inoculation (0 h) and after incubation (24 h), on standard (control) and PHMB-DPL newly produced (0 month), and after 1 and 2 months storage ( <span class="html-fig-inline" id="materials-09-00100-i001"> <img alt="Materials 09 00100 i001" src="/materials/materials-09-00100/article_deploy/html/images/materials-09-00100-i001.png"/></span> Below detection limit).</p> Full article ">Figure 6
<p>Antimicrobial activity of PHMB-HPLs prepared with two different approaches, against <span class="html-italic">E. coli</span> and <span class="html-italic">L. innocua</span> just after inoculation (0 h) and after incubation for 24 h (SS and SSS are the control samples for AS and SAS, respectively; <span class="html-fig-inline" id="materials-09-00100-i002"> <img alt="Materials 09 00100 i002" src="/materials/materials-09-00100/article_deploy/html/images/materials-09-00100-i002.png"/></span>, Below detection limit).</p> Full article ">Figure 7
<p>Antimicrobial properties of PHMB-HPLs produced by two different methods, against <span class="html-italic">E. coli</span> and <span class="html-italic">L. innocua</span> over a period of 30 days simulating daily use (SS and SSS are control samples for AS and SAS, respectively; <span class="html-fig-inline" id="materials-09-00100-i001"> <img alt="Materials 09 00100 i001" src="/materials/materials-09-00100/article_deploy/html/images/materials-09-00100-i001.png"/></span>, Below detection limit).</p> Full article ">Figure 8
<p>Antimicrobial properties against <span class="html-italic">E. coli</span> and <span class="html-italic">L. innocua</span> over a period of 30 days, simulating storage of PHMB-HPLs prepared by two different methods (SS and SSS are control samples for AS and SAS, respectively; <span class="html-fig-inline" id="materials-09-00100-i001"> <img alt="Materials 09 00100 i001" src="/materials/materials-09-00100/article_deploy/html/images/materials-09-00100-i001.png"/></span>, Below detection limit).</p> Full article ">Figure 9
<p>Schematic representation of the antimicrobial evaluation tests: (<b>a</b>) qualitative (disk diffusion method); (<b>b</b>) quantitative [<a href="#B40-materials-09-00100" class="html-bibr">40</a>,<a href="#B41-materials-09-00100" class="html-bibr">41</a>].</p> Full article ">
9155 KiB  
Article
Effect of H2S Plasma Treatment on the Surface Modification of a Polyethylene Terephthalate Surface
by Alenka Vesel, Janez Kovac, Gregor Primc, Ita Junkar and Miran Mozetic
Materials 2016, 9(2), 95; https://doi.org/10.3390/ma9020095 - 5 Feb 2016
Cited by 15 | Viewed by 6028
Abstract
H2S plasma created by an electrode-less radio-frequency discharge was used to modify the surface properties of the polymer polyethylene terephthalate. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities [...] Read more.
H2S plasma created by an electrode-less radio-frequency discharge was used to modify the surface properties of the polymer polyethylene terephthalate. X-ray photoelectron spectroscopy, secondary ion mass spectrometry and atomic force microscopy were used to determine the evolution of the surface functionalities and morphology. A very thin film of chemically bonded sulfur formed on the surface within the first 10 s of treatment, whereas treatment for more than 20 s caused deposition of higher quantities of unbonded sulfur. The sulfur concentration reached a maximum of between 40 and 80 s of plasma treatment; at longer treatment times, the unbonded sulfur vanished, indicating instability of the deposited sulfur layer. Large differences in the surface morphology were observed. Full article
(This article belongs to the Section Biomaterials)
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<p>OES spectra of H<sub>2</sub>S plasma (<b>a</b>) without; and with (<b>b</b>) PET samples.</p> Full article ">Figure 2
<p>XPS surface composition of PET samples treated in H<sub>2</sub>S plasma for various periods.</p> Full article ">Figure 3
<p>Comparison of the high-resolution XPS spectra of the (<b>a</b>) carbon C1s peak; and (<b>b</b>) the sulfur S2p peak at various treatment periods.</p> Full article ">Figure 4
<p>Positive SIMS spectra for (<b>a</b>) untreated PET; and (<b>b</b>) PET treated for 80 s.</p> Full article ">Figure 5
<p>Negative SIMS spectra for (<b>a</b>) untreated PET; and (<b>b</b>) PET treated for 80 s.</p> Full article ">Figure 6
<p>Variation of the relative SIMS intensities of PET fragmented ions: (<b>a</b>) positive; and (<b>b</b>) negative.</p> Full article ">Figure 7
<p>Variation of the relative SIMS intensities of the positive and negative fragments, which are linked with sulfur.</p> Full article ">Figure 8
<p>Sample temperature during plasma treatment.</p> Full article ">Figure 9
<p>AFM images of untreated PET sample: (<b>a</b>) 5 × 5 μm<sup>2</sup>; and (<b>b</b>) 2 × 2 μm<sup>2</sup>.</p> Full article ">Figure 10
<p>AFM images (5 × 5 μm<sup>2</sup>) of samples treated for various periods.</p> Full article ">Figure 11
<p>AFM images (2 × 2 μm<sup>2</sup>) of samples treated for various periods.</p> Full article ">Figure 11 Cont.
<p>AFM images (2 × 2 μm<sup>2</sup>) of samples treated for various periods.</p> Full article ">Figure 12
<p>AFM images (<b>a</b>) 2 × 2 μm<sup>2</sup>; and (<b>b</b>) 5 × 5 μm<sup>2</sup> of the PET sample treated for 80 s after six months of aging.</p> Full article ">Figure 13
<p>Water contact angle variation <span class="html-italic">vs.</span> plasma treatment period.</p> Full article ">Figure 14
<p>Schematic diagram of the experimental system: 1—H<sub>2</sub>S gas source; 2—leak valve; 3—discharge tube; 4—coil; 5—sample; 6—plasma; 7—matching network; 8—RF generator; 9—vacuum gauge; 10—catalyzer; 11—vacuum pump; 12—flange; 13—OES spectrometer.</p> Full article ">
31328 KiB  
Review
How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics
by Sven De Schampheleire, Peter De Jaeger, Kathleen De Kerpel, Bernd Ameel, Henk Huisseune and Michel De Paepe
Materials 2016, 9(2), 94; https://doi.org/10.3390/ma9020094 - 3 Feb 2016
Cited by 44 | Viewed by 10826
Abstract
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most [...] Read more.
This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value). A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically. Full article
(This article belongs to the Special Issue Metal Foams: Synthesis, Characterization and Applications)
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Figure 1

Figure 1
<p>Nomenclature of cast open-cell metal foam.</p> Full article ">Figure 2
<p>Evolution of the yearly number of publications since 1990 as indexed by Google Scholar using the following keywords: “metal foam”, “heat transfer” and “open-cell”.</p> Full article ">Figure 3
<p>Two cast types of open-cell metal foam produced by (<b>a</b>) investment casting from a polyurethane perform and (<b>b</b>) leachable bed casting (example from Alveotec, painted black to increase emissivity).</p> Full article ">Figure 4
<p>An illustration of the axial thickness variation along the strut length for a foam made by Energy Research and Generation (ERG) [<a href="#B34-materials-09-00094" class="html-bibr">34</a>].</p> Full article ">Figure 5
<p>An illustration of the effect of voxel size for a <math display="inline"> <mrow> <mi>μ</mi> <mi>C</mi> <mi>T</mi> </mrow> </math> scan reconstruction with respectively a (<b>a</b>) 37.5 <span class="html-italic">μ</span>m and a (<b>b</b>) 8.5 <span class="html-italic">μ</span>m voxel size. Foam samples are made in-house.</p> Full article ">Figure 6
<p>An illustration of a periodic unit cell from the model of De Jaeger <span class="html-italic">et al.</span> [<a href="#B56-materials-09-00094" class="html-bibr">56</a>] (Foam 1 from <a href="#materials-09-00094-t001" class="html-table">Table 1</a>).</p> Full article ">Figure 7
<p>Permeability (<math display="inline"> <msub> <mi>κ</mi> <mrow> <mo>*</mo> <mo>,</mo> <mi>x</mi> <mi>x</mi> </mrow> </msub> </math>) <span class="html-italic">versus</span> Reynolds number for Foam 1 in <a href="#materials-09-00094-t001" class="html-table">Table 1</a>. The five flow regimes are indicated (I–V).</p> Full article ">Figure 8
<p>Illustration of the different flow regimes as indicated in <a href="#materials-09-00094-f007" class="html-fig">Figure 7</a> and <a href="#materials-09-00094-f009" class="html-fig">Figure 9</a>. (<b>a</b>) Point a: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> <mn>0</mn> <mo>.</mo> <mn>038</mn> </mrow> </math>; (<b>b</b>) Point b: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mo>=</mo> <mn>1</mn> <mo>.</mo> <mn>67</mn> </mrow> </math>; (<b>c</b>) Point c: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mo>=</mo> <mn>16</mn> <mo>.</mo> <mn>9</mn> </mrow> </math>; (<b>d</b>) Point d: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mo>=</mo> <mn>36</mn> <mo>.</mo> <mn>0</mn> </mrow> </math>; (<b>e</b>) Point e: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mo>=</mo> <mn>105</mn> <mo>.</mo> <mn>3</mn> </mrow> </math>; (<b>f</b>) Point f: <math display="inline"> <mrow> <mi>R</mi> <msub> <mi>e</mi> <msub> <mi>d</mi> <mi>s</mi> </msub> </msub> <mo>=</mo> <mn>249</mn> <mo>.</mo> <mn>9</mn> </mrow> </math>.</p> Full article ">Figure 9
<p>Inertial coefficient (<math display="inline"> <msub> <mi>β</mi> <mrow> <mo>*</mo> <mo>,</mo> <mi>x</mi> <mi>x</mi> </mrow> </msub> </math>) <span class="html-italic">versus</span> Reynolds number for Foam 1 in <a href="#materials-09-00094-t001" class="html-table">Table 1</a>.</p> Full article ">Figure 10
<p>Validation of thermal dispersion diffusivity. The symbols + and ∘ represent respectively the <math display="inline"> <msub> <mi>k</mi> <mrow> <mi>d</mi> <mo>,</mo> <mi>x</mi> <mi>x</mi> </mrow> </msub> </math> and <math display="inline"> <msub> <mi>k</mi> <mrow> <mi>d</mi> <mo>,</mo> <mi>y</mi> <mi>y</mi> </mrow> </msub> </math> results. The colors distinguish between data from Calmidi <span class="html-italic">et al.</span> [<a href="#B38-materials-09-00094" class="html-bibr">38</a>] (red), Kaviany [<a href="#B87-materials-09-00094" class="html-bibr">87</a>] (blue), Steven <span class="html-italic">et al.</span> [<a href="#B88-materials-09-00094" class="html-bibr">88</a>] (green) and the CFD results obtained in this work (black).</p> Full article ">Figure 11
<p>Validation of the interstitial heat transfer coefficient. The symbols + and ∘ represent respectively the <math display="inline"> <mrow> <mi>N</mi> <msub> <mi>u</mi> <mi>x</mi> </msub> </mrow> </math> and <math display="inline"> <mrow> <mi>N</mi> <msub> <mi>u</mi> <mi>y</mi> </msub> </mrow> </math> results. The solid line gives correlation (28) [<a href="#B38-materials-09-00094" class="html-bibr">38</a>]. The dashed lines indicate ±15% uncertainty.</p> Full article ">Figure 12
<p>Several foam heat sinks made in-house and used as validation for the VAT model.</p> Full article ">Figure 13
<p>Effectiveness as a function of the number of transfer units (NTU) for mixed-mixed and unmixed-unmixed flow correlations.</p> Full article ">Figure 14
<p>Effectiveness as a function of the number of transfer units (NTU) for mixed-unmixed compared to mixed-mixed and unmixed-unmixed flow correlations.</p> Full article ">
4347 KiB  
Article
Effects of Wet/Dry-Cycling and Plasma Treatments on the Properties of Flax Nonwovens Intended for Composite Reinforcing
by Heura Ventura, Josep Claramunt, Antonio Navarro, Miguel A. Rodriguez-Perez and Mònica Ardanuy
Materials 2016, 9(2), 93; https://doi.org/10.3390/ma9020093 - 3 Feb 2016
Cited by 18 | Viewed by 5371
Abstract
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments [...] Read more.
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force. Full article
(This article belongs to the Special Issue Green Composites)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>SEM images of (<b>a</b>) untreated; and (<b>b</b>) wet/dry cycled flax bundles taken at 10 kV and ×1500 magnification.</p> Full article ">Figure 2
<p>Effect on the surface roughness of the fiber due to increasing time in Ar-plasma treatment of samples: (<b>a</b>) NW C-Ar5; (<b>b</b>) NW C-Ar10; (<b>c</b>) NW C-Ar20; and (<b>d</b>) NW C-Ar30. SEM images were taken at 10 kV and ×10,000 magnification.</p> Full article ">Figure 3
<p>SEM image of the sample NW C-Ar30 taken at 10 kV and ×500 magnification. Arrows mark the craters formed.</p> Full article ">Figure 4
<p>SEM image of surfaces of samples (<b>a</b>) NW C-Cr1010; and (<b>b</b>) NW C-Cr20 taken at 10 kV and ×1500 magnification.</p> Full article ">Figure 5
<p>SEM image of surfaces of samples (<b>a</b>) NW C-Ar5-Et5; (<b>b</b>) NW C-Ar5-Et10; (<b>c</b>) NW C-Cr1010-Et10; and (<b>d</b>) NW C-Et10 taken at 10 kV and ×1500 magnification.</p> Full article ">Figure 6
<p>Comparative SEM images taken at 10 kV and ×10,000 magnification, of the surfaces of samples (<b>a</b>) NW C-Ar5; (<b>b</b>) NW C-Ar5-Et5; and (<b>c</b>) NW C-Ar5-Et10; and (<b>d</b>) NW C-Cr1010; and (<b>e</b>) NW C-Cr1010-Et10.</p> Full article ">Figure 7
<p>Deconvoluted curves of XPS C1s peaks of (<b>a</b>) NW C-Cr1010; and (<b>b</b>) NW C-Cr1010-Et10 samples. CPS stands for counts per second as a measure of the intensity.</p> Full article ">Figure 8
<p>Comparative of the C1s peaks found in the deconvolution curves: (<b>a</b>) for the C1-peaks of all samples; (<b>b</b>) for the C2-peaks; (<b>c</b>) for the C3-peaks; (<b>d</b>) for the C4-peaks.</p> Full article ">Figure 9
<p>Deconvoluted curves of XPS O1s peaks of (<b>a</b>) NW C-Ar5; and (<b>b</b>) NW C-Ar5-Et10 samples.</p> Full article ">Figure 10
<p>TGA curves of selected samples. Curve NW C-Ar20 can be considered the representative curve for all Ar-plasma-treated samples (NW C-Ar5, NW C-Ar10, NW C-Ar30, NW C-Ar5-Et5, and NW C-Ar5-Et10) due to their similarity.</p> Full article ">Figure 11
<p>X-ray diffraction patterns of some selected treated and the untreated samples.</p> Full article ">Figure 12
<p>Breaking force of the NW normalized by the sample weight for comparative purposes only.</p> Full article ">
3329 KiB  
Article
Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites
by Guangwu Zhang, Fuzhong Wang, Jing Dai and Zhixiong Huang
Materials 2016, 9(2), 92; https://doi.org/10.3390/ma9020092 - 2 Feb 2016
Cited by 119 | Viewed by 10050
Abstract
This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized [...] Read more.
This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR. Full article
(This article belongs to the Section Advanced Composites)
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Figure 1

Figure 1
<p>Schematic of the surface treatment of graphene nanoplatelets (GnP) particles with different modifiers.</p> Full article ">Figure 2
<p>Scanning electron microscope (SEM) images of pristine GnP: (<b>a</b>) low magnification and (<b>b</b>) high magnification.</p> Full article ">Figure 3
<p>(<b>a</b>) Fourier transform infrared spectroscopy (FTIR) spectra of treated GnP after subtracting the reference spectrum of the pristine sample GnP; (<b>b</b>) Raman spectra of pristine and treated GnP.</p> Full article ">Figure 4
<p>Tetrahydrofuran (THF) dispersion of pristine GnP (<b>a</b>); aminopropyltriethoxysilane-GnP (APTES-GnP) (<b>b</b>); vinyltrimethoxysilane-GnP (VTMS-GnP) (<b>c</b>); and Triton-GnP (<b>d</b>) after standing for different times: (<b>A</b>) 0 h; (<b>B</b>) 1 h; and (<b>C</b>) 12 h.</p> Full article ">Figure 5
<p>Typical stress-strain curves of neat silicone rubber (SR) and the composites filled with various GnP.</p> Full article ">Figure 6
<p>Field emission scanning electron microscopy (ESEM) images of the tensile fracture surfaces of neat SR and the composites: (<b>a</b>) SR; (<b>b</b>) pristine GnP/SR; (<b>c</b>) APTES-GnP/SR; (<b>d</b>) VTMS-GnP/SR; and (<b>e</b>) Triton-GnP/SR composites.</p> Full article ">Figure 7
<p>Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA) curves of neat SR and the composites with different GnP measured in nitrogen atmosphere: (<b>a</b>) TGA curves and (<b>b</b>) DTGA curves.</p> Full article ">Figure 8
<p>Crystallization (<b>a</b>) and melting (<b>b</b>) curves of neat SR and the composites with different GnP.</p> Full article ">Figure 9
<p>Thermal conductivity of neat SR, pristine GnP, APTES-GnP, VTMS-GnP and Triton-GnP composites.</p> Full article ">
3289 KiB  
Article
Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete
by Antonio López-Uceda, Jesús Ayuso, José Ramón Jiménez, Francisco Agrela, Auxiliadora Barbudo and Jorge De Brito
Materials 2016, 9(2), 91; https://doi.org/10.3390/ma9020091 - 2 Feb 2016
Cited by 20 | Viewed by 5323
Abstract
This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures [...] Read more.
This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content. Full article
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<p>Grain size distribution of aggregates used.</p> Full article ">Figure 2
<p>Slab execution, specimens cast and core extraction and non-destructive test.</p> Full article ">Figure 3
<p>Compressive strength in cast specimens at 7, 28, 90 and 180 days.</p> Full article ">Figure 4
<p>Compressive strength in cast specimens at 28 days obtained by several authors in concrete with full MRA replacement.</p> Full article ">Figure 5
<p>Relative compressive and splitting tensile strength in cast specimens at 28 days obtained by Silva <span class="html-italic">et al.</span>’s review in concrete with MRA.</p> Full article ">Figure 6
<p>Compressive strength in core concrete relative to that of CC at 28 days.</p> Full article ">Figure 7
<p>Correlation between compressive strength of concrete cores and cast specimens.</p> Full article ">Figure 8
<p>Splitting tensile strength in cast specimens at 7, 28 and 90 days.</p> Full article ">Figure 9
<p>Splitting tensile strength in core concrete relative to that of CC at 28 days.</p> Full article ">Figure 10
<p>Modulus of elasticity in cast specimens with MRA incorporation ratio at 28 days.</p> Full article ">Figure 11
<p>Evolution of the UPV test over the long term.</p> Full article ">Figure 12
<p>Comparison of UPV relative to that of CC with that of other authors.</p> Full article ">Figure 13
<p>Rebound number at 7, 28 and 90 days.</p> Full article ">Figure 14
<p>Rebound number at 7, 28 and 90 days.</p> Full article ">
7355 KiB  
Article
Heterojunctions of p-BiOI Nanosheets/n-TiO2 Nanofibers: Preparation and Enhanced Visible-Light Photocatalytic Activity
by Kexin Wang, Changlu Shao, Xinghua Li, Fujun Miao, Na Lu and Yichun Liu
Materials 2016, 9(2), 90; https://doi.org/10.3390/ma9020090 - 30 Jan 2016
Cited by 38 | Viewed by 7935
Abstract
p-BiOI nanosheets/n-TiO2 nanofibers (p-BiOI/n-TiO2 NFs) have been facilely prepared via the electrospinning technique combining successive ionic layer adsorption and reaction (SILAR). Dense BiOI nanosheets with good crystalline and width about 500 nm were uniformly assembled on TiO2 nanofibers at room [...] Read more.
p-BiOI nanosheets/n-TiO2 nanofibers (p-BiOI/n-TiO2 NFs) have been facilely prepared via the electrospinning technique combining successive ionic layer adsorption and reaction (SILAR). Dense BiOI nanosheets with good crystalline and width about 500 nm were uniformly assembled on TiO2 nanofibers at room temperature. The amount of the heterojunctions and the specific surface area were well controlled by adjusting the SILAR cycles. Due to the synergistic effect of p-n heterojunctions and high specific surface area, the obtained p-BiOI/n-TiO2 NFs exhibited enhanced visible-light photocatalytic activity. Moreover, the p-BiOI/n-TiO2 NFs heterojunctions could be easily recycled without decreasing the photocatalytic activity owing to their one-dimensional nanofibrous structure. Based on the above, the heterojunctions of p-BiOI/n-TiO2 NFs may be promising visible-light-driven photocatalysts for converting solar energy to chemical energy in environment remediation. Full article
(This article belongs to the Special Issue Photovoltaic Materials and Electronic Devices)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>(<b>a</b>) SEM images of TiO<sub>2</sub> nanofibers; (<b>b</b>) BiOI/TiO<sub>2</sub>-C10; (<b>c</b>) BiOI/TiO<sub>2</sub>-C20; and (<b>d</b>) BiOI/TiO<sub>2</sub>-C30 at low magnification and high magnification (insets).</p> Full article ">Figure 2
<p>(<b>a</b>) TEM; and (<b>b</b>) HRTEM images of BiOI/TiO<sub>2</sub>-C30.</p> Full article ">Figure 3
<p>XRD patterns of different samples.</p> Full article ">Figure 4
<p>(<b>a</b>) XPS spectra of Bi 4f; (<b>b</b>) I 3d; and (<b>c</b>) O 1s for BiOI/TiO<sub>2</sub>-C30; (<b>d</b>) XPS spectra of Ti 2p for TiO<sub>2</sub> nanofibers (bottom) and BiOI/TiO<sub>2</sub>-C30 (top).</p> Full article ">Figure 5
<p>Typical N<sub>2</sub> gas adsorption desorption isotherms of different samples and their corresponding pore-size distributions (inset).</p> Full article ">Figure 6
<p>UV-vis absorption spectra of different samples.</p> Full article ">Figure 7
<p>(<b>a</b>) Degradation curves of MO under visible light irradiation; and (<b>b</b>) the apparent first-order kinetics fitting over different samples.</p> Full article ">Figure 8
<p>Photocatalysis tests of BiOI/TiO<sub>2</sub>-C30 for three cycles.</p> Full article ">Figure 9
<p>Possible photocatalytic reactions of p-BiOI/n-TiO<sub>2</sub> NFs heterojunctions.</p> Full article ">Figure 10
<p>Schematic illustration for the preparation of p-BiOI/n-TiO<sub>2</sub> NFs heterojunctions.</p> Full article ">
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